Uber Go Style Guide
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Uber Go Style Guide
Table of Contents
-
- Pointers to Interfaces
- Receivers and Interfaces
- Zero-value Mutexes are Valid
- Copy Slices and Maps at Boundaries
- Channel Size is One or None
- Handle Type Assertion Failures
- Use go.uber.org/atomic
-
- Prefer strconv over fmt
- Avoid string-to-byte conversion
-
- Group Similar Declarations
- Import Group Ordering
- Function Grouping and Ordering
- Top-level Variable Declarations
- Prefix Unexported Globals with _
- Use Field Names to initialize Structs
- Local Variable Declarations
- Reduce Scope of Variables
- Avoid Naked Parameters
- Use Raw String Literals to Avoid Escaping
- Initializing Struct References
- Format Strings outside Printf
- Naming Printf-style Functions
Introduction
Styles are the conventions that govern our code. The term style is a bit of a misnomer, since these conventions cover far more than just source file formatting—gofmt handles that for us.
The goal of this guide is to manage this complexity by describing in detail the Dos and Don'ts of writing Go code at Uber. These rules exist to keep the code base manageable while still allowing engineers to use Go language features productively.
This guide was originally created by Prashant Varanasi and Simon Newton as a way to bring some colleagues up to speed with using Go. Over the years it has been amended based on feedback from others.
This documents idiomatic conventions in Go code that we follow at Uber. A lot of these are general guidelines for Go, while others extend upon external resources:
All code should be error-free when run through golint
and go vet
. We
recommend setting up your editor to:
-
Run
goimports
on save -
Run
golint
andgo vet
to check for errors
You can find information in editor support for Go tools here: https://github.com/golang/go/wiki/IDEsAndTextEditorPlugins
Guidelines
Pointers to Interfaces
You almost never need a pointer to an interface. You should be passing interfaces as values—the underlying data can still be a pointer.
An interface is two fields:
- A pointer to some type-specific information. You can think of this as "type."
- Data pointer. If the data stored is a pointer, it’s stored directly. If the data stored is a value, then a pointer to the value is stored.
If you want interface methods to modify the underlying data, you must use a pointer.
Receivers and Interfaces
Methods with value receivers can be called on pointers as well as values.
For example,
type S struct { data string } func (s S) Read() string { return s.data } func (s *S) Write(str string) { s.data = str } sVals := map[int]S{1: {"A"}} // You can only call Read using a value sVals[1].Read() // This will not compile: // sVals[0].Write("test") sPtrs := map[int]*S{1: {"A"}} // You can call both Read and Write using a pointer sPtrs[1].Read() sPtrs[1].Write("test")
Similarly, an interface can be satisfied by a pointer, even if the method has a value receiver.
type F interface { f() } type S1 struct{} func (s S1) f() {} type S2 struct{} func (s *S2) f() {} s1Val := S1{} s1Ptr := &S1{} s2Val := S2{} s2Ptr := &S2{} var i F i = s1Val i = s1Ptr i = s2Ptr // The following doesn't compile, since s2Val is a value, and there is no value receiver for f. // i = s2Val
Effective Go has a good write up on Pointers vs. Values .
Zero-value Mutexes are Valid
The zero-value of sync.Mutex
and sync.RWMutex
is valid, so you almost
never need a pointer to a mutex.
mu := new(sync.Mutex) mu.Lock()
var mu sync.Mutex mu.Lock()
If you use a struct by pointer, then the mutex can be a non-pointer field or, preferably, embedded directly into the struct.
type smap struct { sync.Mutex data map[string]string } func newSMap() *smap { return &smap{ data: make(map[string]string), } } func (m *smap) Get(k string) string { m.Lock() defer m.Unlock() return m.data[k] }
type SMap struct { mu sync.Mutex data map[string]string } func NewSMap() *SMap { return &SMap{ data: make(map[string]string), } } func (m *SMap) Get(k string) string { m.mu.Lock() defer m.mu.Unlock() return m.data[k] }Embed for private types or types that need to implement the Mutex interface. For exported types, use a private lock.
Copy Slices and Maps at Boundaries
Slices and maps contain pointers to the underlying data so be wary of scenarios when they need to be copied.
Receiving Slices and Maps
Keep in mind that users can modify a map or slice you received as an argument if you store a reference to it.
Bad Goodfunc (d *Driver) SetTrips(trips []Trip) { d.trips = trips } trips := ... d1.SetTrips(trips) // Did you mean to modify d1.trips? trips[0] = ...
func (d *Driver) SetTrips(trips []Trip) { d.trips = make([]Trip, len(trips)) copy(d.trips, trips) } trips := ... d1.SetTrips(trips) // We can now modify trips[0] without affecting d1.trips. trips[0] = ...
Returning Slices and Maps
Similarly, be wary of user modifications to maps or slices exposing internal state.
Bad Goodtype Stats struct { sync.Mutex counters map[string]int } // Snapshot returns the current stats. func (s *Stats) Snapshot() map[string]int { s.Lock() defer s.Unlock() return s.counters } // snapshot is no longer protected by the lock! snapshot := stats.Snapshot()
type Stats struct { sync.Mutex counters map[string]int } func (s *Stats) Snapshot() map[string]int { s.Lock() defer s.Unlock() result := make(map[string]int, len(s.counters)) for k, v := range s.counters { result[k] = v } return result } // Snapshot is now a copy. snapshot := stats.Snapshot()
Defer to Clean Up
Use defer to clean up resources such as files and locks.
Bad Goodp.Lock() if p.count < 10 { p.Unlock() return p.count } p.count++ newCount := p.count p.Unlock() return newCount // easy to miss unlocks due to multiple returns
p.Lock() defer p.Unlock() if p.count < 10 { return p.count } p.count++ return p.count // more readable
Defer has an extremely small overhead and should be avoided only if you can
prove that your function execution time is in the order of nanoseconds. The
readability win of using defers is worth the miniscule cost of using them. This
is especially true for larger methods that have more than simple memory
accesses, where the other computations are more significant than the defer
.
Channel Size is One or None
Channels should usually have a size of one or be unbuffered. By default, channels are unbuffered and have a size of zero. Any other size must be subject to a high level of scrutiny. Consider how the size is determined, what prevents the channel from filling up under load and blocking writers, and what happens when this occurs.
Bad Good// Ought to be enough for anybody! c := make(chan int, 64)
// Size of one c := make(chan int, 1) // or // Unbuffered channel, size of zero c := make(chan int)
Start Enums at One
The standard way of introducing enumerations in Go is to declare a custom type
and a const
group with iota
. Since variables have a 0 default value, you
should usually start your enums on a non-zero value.
type Operation int const ( Add Operation = iota Subtract Multiply ) // Add=0, Subtract=1, Multiply=2
type Operation int const ( Add Operation = iota + 1 Subtract Multiply ) // Add=1, Subtract=2, Multiply=3
There are cases where using the zero value makes sense, for example when the zero value case is the desirable default behavior.
type LogOutput int const ( LogToStdout LogOutput = iota LogToFile LogToRemote ) // LogToStdout=0, LogToFile=1, LogToRemote=2
Error Types
There are various options for declaring errors:
-
errors.New
for errors with simple static strings -
fmt.Errorf
for formatted error strings -
Custom types that implement an
Error()
method -
Wrapped errors using
"pkg/errors".Wrap
When returning errors, consider the following to determine the best choice:
-
Is this a simple error that needs no extra information? If so,
errors.New
should suffice. -
Do the clients need to detect and handle this error? If so, you should use a
custom type, and implement the
Error()
method. - Are you propagating an error returned by a downstream function? If so, check thesection on error wrapping.
-
Otherwise,
fmt.Errorf
is okay.
If the client needs to detect the error, and you have created a simple error
using
errors.New
, use a var for the error.
// package foo func Open() error { return errors.New("could not open") } // package bar func use() { if err := foo.Open(); err != nil { if err.Error() == "could not open" { // handle } else { panic("unknown error") } } }
// package foo var ErrCouldNotOpen = errors.New("could not open") func Open() error { return ErrCouldNotOpen } // package bar if err := foo.Open(); err != nil { if err == foo.ErrCouldNotOpen { // handle } else { panic("unknown error") } }
If you have an error that clients may need to detect, and you would like to add more information to it (e.g., it is not a static string), then you should use a custom type.
Bad Goodfunc open(file string) error { return fmt.Errorf("file %q not found", file) } func use() { if err := open(); err != nil { if strings.Contains(err.Error(), "not found") { // handle } else { panic("unknown error") } } }
type errNotFound struct { file string } func (e errNotFound) Error() string { return fmt.Sprintf("file %q not found", e.file) } func open(file string) error { return errNotFound{file: file} } func use() { if err := open(); err != nil { if _, ok := err.(errNotFound); ok { // handle } else { panic("unknown error") } } }
Be careful with exporting custom error types directly since they become part of the public API of the package. It is preferable to expose matcher functions to check the error instead.
// package foo type errNotFound struct { file string } func (e errNotFound) Error() string { return fmt.Sprintf("file %q not found", e.file) } func IsNotFoundError(err error) bool { _, ok := err.(errNotFound) return ok } func Open(file string) error { return errNotFound{file: file} } // package bar if err := foo.Open("foo"); err != nil { if foo.IsNotFoundError(err) { // handle } else { panic("unknown error") } }
Error Wrapping
There are three main options for propagating errors if a call fails:
- Return the original error if there is no additional context to add and you want to maintain the original error type.
-
Add context using
"pkg/errors".Wrap
so that the error message provides more context and"pkg/errors".Cause
can be used to extract the original error. -
Use
fmt.Errorf
if the callers do not need to detect or handle that specific error case.
It is recommended to add context where possible so that instead of a vague error such as "connection refused", you get more useful errors such as "failed to call service foo: connection refused".
See also Don't just check errors, handle them gracefully .
Handle Type Assertion Failures
The single return value form of a type assertion will panic on an incorrect type. Therefore, always use the "comma ok" idiom.
Bad Goodt := i.(string)
t, ok := i.(string) if !ok { // handle the error gracefully }
Don't Panic
Code running in production must avoid panics. Panics are a major source of cascading failures . If an error occurs, the function must return an error and allow the caller to decide how to handle it.
Bad Goodfunc foo(bar string) { if len(bar) == 0 { panic("bar must not be empty") } // ... } func main() { if len(os.Args) != 2 { fmt.Println("USAGE: foo <bar>") os.Exit(1) } foo(os.Args[1]) }
func foo(bar string) error { if len(bar) == 0 return errors.New("bar must not be empty") } // ... return nil } func main() { if len(os.Args) != 2 { fmt.Println("USAGE: foo <bar>") os.Exit(1) } if err := foo(os.Args[1]); err != nil { panic(err) } }
Panic/recover is not an error handling strategy. A program must panic only when something irrecoverable happens such as a nil dereference. An exception to this is program initialization: bad things at program startup that should abort the program may cause panic.
var _statusTemplate = template.Must(template.New("name").Parse("_statusHTML"))
Even in tests, prefer t.Fatal
or t.FailNow
over panics to ensure that the
test is marked as failed.
// func TestFoo(t *testing.T) f, err := ioutil.TempFile("", "test") if err != nil { panic("failed to set up test") }
// func TestFoo(t *testing.T) f, err := ioutil.TempFile("", "test") if err != nil { t.Fatal("failed to set up test") }
Use go.uber.org/atomic
Atomic operations with the sync/atomic
package operate on the raw types
( int32
, int64
, etc.) so it is easy to forget to use the atomic operation to
read or modify the variables.
go.uber.org/atomic
adds type safety to these operations by hiding the
underlying type. Additionally, it includes a convenient atomic.Bool
type.
type foo struct { running int32 // atomic } func (f* foo) start() { if atomic.SwapInt32(&f.running, 1) == 1 { // already running… return } // start the Foo } func (f *foo) isRunning() bool { return f.running == 1 // race! }
type foo struct { running atomic.Bool } func (f *foo) start() { if f.running.Swap(true) { // already running… return } // start the Foo } func (f *foo) isRunning() bool { return f.running.Load() }
Performance
Performance-specific guidelines apply only to the hot path.
Prefer strconv over fmt
When converting primitives to/from strings, strconv
is faster than fmt
.
var i int = ... s := fmt.Sprint(i)
var i int = ... s := strconv.Itoa(i)
Avoid string-to-byte conversion
Do not create byte slices from a fixed string repeatedly. Instead, perform the conversion once and capture the result.
Bad Goodfor i := 0; i < b.N; i++ { w.Write([]byte("Hello world")) }
data := []byte("Hello world") for i := 0; i < b.N; i++ { w.Write(data) }
BenchmarkBad-4 50000000 22.2 ns/op
BenchmarkGood-4 500000000 3.25 ns/op
Style
Group Similar Declarations
Go supports grouping similar declarations.
Bad Goodimport "a" import "b"
import ( "a" "b" )
This also applies to constants, variables, and type declarations.
Bad Goodconst a = 1 const b = 2 var a = 1 var b = 2 type Area float64 type Volume float64
const ( a = 1 b = 2 ) var ( a = 1 b = 2 ) type ( Area float64 Volume float64 )
Only group related declarations. Do not group declarations that are unrelated.
Bad Goodtype Operation int const ( Add Operation = iota + 1 Subtract Multiply ENV_VAR = "MY_ENV" )
type Operation int const ( Add Operation = iota + 1 Subtract Multiply ) const ENV_VAR = "MY_ENV"
Groups are not limited in where they can be used. For example, you can use them inside of functions.
Bad Goodfunc f() string { var red = color.New(0xff0000) var green = color.New(0x00ff00) var blue = color.New(0x0000ff) ... }
func f() string { var ( red = color.New(0xff0000) green = color.New(0x00ff00) blue = color.New(0x0000ff) ) ... }
Import Group Ordering
There should be two import groups:
- Standard library
- Everything else
This is the grouping applied by goimports by default.
Bad Goodimport ( "fmt" "os" "go.uber.org/atomic" "golang.org/x/sync/errgroup" )
import ( "fmt" "os" "go.uber.org/atomic" "golang.org/x/sync/errgroup" )
Package Names
When naming packages, choose a name that is,
- All lower-case. No capitals or underscores.
- Does not need to be renamed using named imports at most call sites.
- Short and succint. Remember that the name is identified in full at every call site.
-
Not plural. For example,
net/url
, notnet/urls
. - Not "common", "util", "shared", or "lib". These are bad, uninformative names.
See also Package Names and Style guideline for Go packages .
Function Names
We follow the Go community's convention of using MixedCaps for function
names
. An exception is made for test functions, which may contain underscores
for the purpose of grouping related test cases, e.g., TestMyFunction_WhatIsBeingTested
.
Import Aliasing
Import aliasing must be used if the package name does not match the last element of the import path.
import ( "net/http" client "example.com/client-go" trace "example.com/trace/v2" )
In all other scenarios, import aliases should be avoided unless there is a direct conflict between imports.
Bad Goodimport ( "fmt" "os" nettrace "golang.net/x/trace" )
import ( "fmt" "os" "runtime/trace" nettrace "golang.net/x/trace" )
Function Grouping and Ordering
- Functions should be sorted in rough call order.
- Functions in a file should be grouped by receiver.
Therefore, exported functions should appear first in a file, after struct
, const
, var
definitions.
A newXYZ()
/ NewXYZ()
may appear after the type is defined, but before the
rest of the methods on the receiver.
Since functions are grouped by receiver, plain utility functions should appear towards the end of the file.
Bad Goodfunc (s *something) Cost() { return calcCost(s.weights) } type something struct{ ... } func calcCost(n int[]) int {...} func (s *something) Stop() {...} func newSomething() *something { return &something{} }
type something struct{ ... } func newSomething() *something { return &something{} } func (s *something) Cost() { return calcCost(s.weights) } func (s *something) Stop() {...} func calcCost(n int[]) int {...}
Reduce Nesting
Code should reduce nesting where possible by handling error cases/special conditions first and returning early or continuing the loop. Reduce the amount of code that is nested multiple levels.
Bad Goodfor _, v := range data { if v.F1 == 1 { v = process(v) if err := v.Call(); err == nil { v.Send() } else { return err } } else { log.Printf("Invalid v: %v", v) } }
for _, v := range data { if v.F1 != 1 { log.Printf("Invalid v: %v", v) continue } v = process(v) if err := v.Call(); err != nil { return err } v.Send() }
Unnecessary Else
If a variable is set in both branches of an if, it can be replaced with a single if.
Bad Goodvar a int if b { a = 100 } else { a = 10 }
a := 10 if b { a = 100 }
Top-level Variable Declarations
At the top level, use the standard var
keyword. Do not specify the type,
unless it is not the same type as the expression.
var _s string = F() func F() string { return "A" }
var _s = F() // Since F already states that it returns a string, we don't need to specify // the type again. func F() string { return "A" }
Specify the type if the type of the expression does not match the desired type exactly.
type myError struct{} func (myError) Error() string { return "error" } func F() myError { return myError{} } var _e error = F() // F returns an object of type myError but we want error.
Prefix Unexported Globals with _
Prefix unexported top-level var
s and const
s with _
to make it clear when
they are used that they are global symbols.
Exception: Unexported error values, which should be prefixed with err
.
Rationale: Top-level variables and constants have a package scope. Using a generic name makes it easy to accidentally use the wrong value in a different file.
Bad Good// foo.go const ( defaultPort = 8080 defaultUser = "user" ) // bar.go func Bar() { defaultPort := 9090 ... fmt.Println("Default port", defaultPort) // We will not see a compile error if the first line of // Bar() is deleted. }
// foo.go const ( _defaultPort = 8080 _defaultUser = "user" )
Embedding in Structs
Embedded types (such as mutexes) should be at the top of the field list of a struct, and there must be an empty line separating embedded fields from regular fields.
Bad Goodtype Client struct { version int http.Client }
type Client struct { http.Client version int }
Use Field Names to initialize Structs
You should almost always specify field names when initializing structs. This is
now enforced by
go vet
.
k := User{"John", "Doe", true}
k := User{ FirstName: "John", LastName: "Doe", Admin: true, }
Exception: Field names may be omitted in test tables when there are 3 or fewer fields.
tests := []struct{ }{ op Operation want string }{ {Add, "add"}, {Subtract, "subtract"}, }
Local Variable Declarations
Short variable declarations ( :=
) should be used if a variable is being set to
some value explicitly.
var s = "foo"
s := "foo"
However, there are cases where the default value is clearer when the var
keyword is use. Declaring Empty Slices
, for example.
func f(list []int) { filtered := []int{} for _, v := range list { if v > 10 { filtered = append(filtered, v) } } }
func f(list []int) { var filtered []int for _, v := range list { if v > 10 { filtered = append(filtered, v) } } }
nil is a valid slice
nil
is a valid slice of length 0. This means that,
-
You should not return a slice of length zero explicitly. Return
Bad Goodnil
instead.if x == "" { return []int{} }
if x == "" { return nil }
-
To check if a slice is empty, always use
Bad Goodlen(s) == 0
. Do not check fornil
.func isEmpty(s []string) bool { return s == nil }
func isEmpty(s []string) bool { return len(s) == 0 }
-
The zero value (a slice declared with
Bad Goodvar
) is usable immediately withoutmake()
.nums := []int{} // or, nums := make([]int) if add1 { nums = append(nums, 1) } if add2 { nums = append(nums, 2) }
var nums []int if add1 { nums = append(nums, 1) } if add2 { nums = append(nums, 2) }
Reduce Scope of Variables
Where possible, reduce scope of variables. Do not reduce the scope if it conflicts with.
Bad Gooderr := f.Close() if err != nil { return err }
if err := f.Close(); err != nil { return err }
If you need a result of a function call outside of the if, then you should not try to reduce the scope.
Bad Goodif f, err := os.Open("f"); err == nil { _, err = io.WriteString(f, "data") if err != nil { return err } return f.Close() } else { return err }
f, err := os.Open("f") if err != nil { return err } if _, err := io.WriteString(f, "data"); err != nil { return err } return f.Close()
Avoid Naked Parameters
Naked parameters in function calls can hurt readability. Add C-style comments
( /* ... */
) for parameter names when their meaning is not obvious.
// func printInfo(name string, isLocal, done bool) printInfo("foo", true, true)
// func printInfo(name string, isLocal, done bool) printInfo("foo", true /* isLocal */, true /* done */)
Better yet, replace naked bool
types with custom types for more readable and
type-safe code. This allows more than just two states (true/false) for that
parameter in the future.
type Region int const ( UnknownRegion Region = iota Local ) type Status int const ( StatusReady = iota + 1 StatusDone // Maybe we will have a StatusInProgress in the future. ) func printInfo(name string, region Region, status Status)
Use Raw String Literals to Avoid Escaping
Go supports raw string literals , which can span multiple lines and include quotes. Use these to avoid hand-escaped strings which are much harder to read.
Bad GoodwantError := "unknown name:\"test\""
wantError := `unknown error:"test"`
Initializing Struct References
Use &T{}
instead of new(T)
when initializing struct references so that it
is consistent with the struct initialization.
sval := T{Name: "foo"} // inconsistent sptr := new(T) sptr.Name = "bar"
sval := T{Name: "foo"} sptr := &T{Name: "bar"}
Format Strings outside Printf
If you declare format strings for Printf
-style functions outside a string
literal, make them const
values.
This helps go vet
perform static analysis of the format string.
msg := "unexpected values %v, %v\n" fmt.Printf(msg, 1, 2)
const msg = "unexpected values %v, %v\n" fmt.Printf(msg, 1, 2)
Naming Printf-style Functions
When you declare a Printf
-style function, make sure that go vet
can detect
it and check the format string.
This means that you should use pre-defined Printf
-style function
names if possible. go vet
will check these by default. See Printf family
for more information.
If using the pre-defined names is not an option, end the name you choose with
f: Wrapf
, not Wrap
. go vet
can be asked to check specific Printf
-style
names but they must end with f.
$ go vet -printfuncs=wrapf,statusf
See also go vet: Printf family check .
Patterns
Test Tables
Use table-driven tests with subtests to avoid duplicating code when the core test logic is repetitive.
Bad Good// func TestSplitHostPort(t *testing.T) host, port, err := net.SplitHostPort("192.0.2.0:8000") require.NoError(t, err) assert.Equal(t, "192.0.2.0", host) assert.Equal(t, "8000", port) host, port, err = net.SplitHostPort("192.0.2.0:http") require.NoError(t, err) assert.Equal(t, "192.0.2.0", host) assert.Equal(t, "http", port) host, port, err = net.SplitHostPort(":8000") require.NoError(t, err) assert.Equal(t, "", host) assert.Equal(t, "8000", port) host, port, err = net.SplitHostPort("1:8") require.NoError(t, err) assert.Equal(t, "1", host) assert.Equal(t, "8", port)
// func TestSplitHostPort(t *testing.T) tests := []struct{ give string wantHost string wantPort string }{ { give: "192.0.2.0:8000", wantHost: "192.0.2.0", wantPort: "8000", }, { give: "192.0.2.0:http", wantHost: "192.0.2.0", wantPort: "http", }, { give: ":8000", wantHost: "", wantPort: "8000", }, { give: "1:8", wantHost: "1", wantPort: "8", }, } for _, tt := range tests { t.Run(tt.give, func(t *testing.T) { host, port, err := net.SplitHostPort(tt.give) require.NoError(t, err) assert.Equal(t, tt.wantHost, host) assert.Equal(t, tt.wantPort, port) }) }
Test tables make it easier to add context to error messages, reduce duplicate logic, and add new test cases.
We follow the convention that the slice of structs is referred to as tests
and each test case tt
. Further, we encourage explicating the input and output
values for each test case with give
and want
prefixes.
tests := []struct{ give string wantHost string wantPort string }{ // ... } for _, tt := range tests { // ... }
Functional Options
Functional options is a pattern in which you declare an opaque Option
type
that records information in some internal struct. You accept a variadic number
of these options and act upon the full information recorded by the options on
the internal struct.
Use this pattern for optional arguments in constructors and other public APIs that you foresee needing to expand, especially if you already have three or more arguments on those functions.
Bad Good// package db func Connect( addr string, timeout time.Duration, caching bool, ) (*Connection, error) { // ... } // Timeout and caching must always be provided, // even if the user wants to use the default. db.Connect(addr, db.DefaultTimeout, db.DefaultCaching) db.Connect(addr, newTimeout, db.DefaultCaching) db.Connect(addr, db.DefaultTimeout, false /* caching */) db.Connect(addr, newTimeout, false /* caching */)
type options struct { timeout time.Duration caching bool } // Option overrides behavior of Connect. type Option interface { apply(*options) } type optionFunc func(*options) func (f optionFunc) apply(o *options) { f(o) } func WithTimeout(t time.Duration) Option { return optionFunc(func(o *options) { o.timeout = t }) } func WithCaching(cache bool) Option { return optionFunc(func(o *options) { o.caching = cache }) } // Connect creates a connection. func Connect( addr string, opts ...Option, ) (*Connection, error) { options := options{ timeout: defaultTimeout, caching: defaultCaching, } for _, o := range opts { o.apply(&options) } // ... } // Options must be provided only if needed. db.Connect(addr) db.Connect(addr, db.WithTimeout(newTimeout)) db.Connect(addr, db.WithCaching(false)) db.Connect( addr, db.WithCaching(false), db.WithTimeout(newTimeout), )
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