Slice pre-allocation

#tips #tricks

Did you know that it’s possible to use a pre-allocated slice without specifying the length of the array (zero). This allows us to use append just like we would:

// instead of
a := make([]int, 10)
a[0] = 1

// use this
b := make([]int, 0, 10)
b = append(b, 1)

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers

Chaining technique

#tips #tricks

The technique of chaining can be applied to function (pointer) receivers. To illustrate this, let’s consider a Person struct with two functions, AddAge and Rename, that can be used to modify it.

type Person struct {
  Name string
  Age  int
}

func (p *Person) AddAge() {
  p.Age++
}

func (p *Person) Rename(name string) {
  p.Name = name
}

If you’re looking to add age to a person and then rename them, the typical approach is as follows:

func main() {
  p := Person{Name: "Aiden", Age: 30}

  p.AddAge()
  p.Rename("Aiden 2")
}

Alternatively, we can modify the AddAge and Rename function receivers to return the modified object itself, even if they don’t typically return anything.

func (p *Person) AddAge() *Person {
  p.Age++
  return p
}

func (p *Person) Rename(name string) *Person {
  p.Name = name
  return p
}

By returning the modified object itself, we can easily chain multiple function receivers together without having to add unnecessary lines of code:

p = p.AddAge().Rename("Aiden 2")

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers

Using import with ‘_’ for package initialization

#tips #tricks

Sometimes, in libraries, you may come across import statements that combine an underscore (_) like this:

import ( _ "google.golang.org/genproto/googleapis/api/annotations" )

This will execute the initialization code (init function) of the package, without creating a name reference for it. This allows you to initialize packages, register connections, and perform other tasks before running the code.

Let’s consider an example to better understand how it works:

// underscore
package underscore

func init() {
  fmt.Println("init called from underscore package")
}
// mainpackage main 
import (
  _ "lab/underscore"
)
func main() {}
// log: init called from underscore package

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers

Use import with dot .

#tips #tricks

Having explored how we can use import with underscore, let’s now look at how the dot . operator is more commonly used.

As a developer, the dot . operator can be used to make the exported identifiers of an imported package available without having to specify the package name, which can be a helpful shortcut for lazy developers.

Pretty cool, right? This is especially useful when dealing with long package names in our projects, such as externalmodel or doingsomethinglonglib

To demonstrate, here’s a brief example:

package main

import (
  "fmt"
  . "math"
)

func main() {
  fmt.Println(Pi) // 3.141592653589793
  fmt.Println(Sin(Pi / 2)) // 1
}

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers

Ternary with generic

#tips #tricks

Go does not have built-in support for ternary operators like many other programming languages:

# python 
min = a if a < b else b

# c#
min = x < y ? x : y

With Go’s generics in version 1.18, we now have the ability to create a utility that allows for ternary-like functionality in just a single line of code:

// our utility
func Ter[T any](cond bool, a, b T) T {
  if cond {
    return a
  }
  
  return b
}

func main() {
  fmt.Println(Ter(true, 1, 2)) // 1 
  fmt.Println(Ter(false, 1, 2)) // 2
}

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers

Synchronize a map

#tips #tricks

To synchronize a map, you will see code that uses a sync.Mutex or sync.RWMutex.

You gain some benefits using a sync.RWMutex with read-heavy operations on the map.

var (
  s map[int]bool
  m sync.RWMutex
)

for i := 0; i < 7; i++ {
  go func(i int) {
    m.Lock()
    defer m.Unlock()
    s[i] = true
  }(i)
}

// Elsewhere
m.RLock()
for k, v := range s {
  fmt.Println(k, v)
}
m.RUnlock()

Instead of using a map mutex pair, you can use sync.Map:

var s sync.Map

for i := 0; i < 7; i++ {
  go func(i int) {
    s.Store(i, true)
  }(i)
}

// Elsewhere
s.Range(func(k, v any) bool {
  fmt.Println(k.(int), v.(bool))
  return true
})

If you feel uneasy about the use of any in all sync.Map functions, you could define a generic wrapper:

type Map[K any, V any] struct {
  m sync.Map
}

func (m *Map[K, V]) Load(key K) (V, bool) {
  v, ok := m.m.Load(key)
  return v.(V), ok
}

func (m *Map[K, V]) Range(fn func(key K, value V) bool) {
  m.m.Range(func(key, value any) bool {
    return fn(key.(K), value.(V))
  })
}

func (m *Map[K, V]) Store(key K, value V) {
  m.m.Store(key, value)
}

And then use the wrapper instead:

var s Map[int, bool]

for i := 0; i < 7; i++ {
  go func(i int) {
    s.Store(i, true)
  }(i)
}

// Elsewhere
s.Range(func(k int, v bool) bool {
  fmt.Println(k, v)
  return true
})

One caveat is that the Range function is different from holding a lock around the range loop in the sync.RWMutex example. Range does not necessarily correspond to any consistent snapshot of the map’s contents.

➖➖➖➖➖➖➖➖
🕊 @gopher_academy | @GolangEngineers