🐹 Golang for TypeScript developers

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A guide to Go (Golang) for developers coming from TypeScript/JavaScript.

Key differences from TypeScript Jump to heading

Concept	TypeScript	Go
Typing	Structural, gradual	Structural, static
Compilation	Transpiles to JS	Compiles to native binary
Null handling	null / undefined	Zero values, no null
Generics	Full support	Added in Go 1.18
Package manager	npm/yarn/pnpm	Go modules
Concurrency	Async/await, Promises	Goroutines, channels

Variables and constants Jump to heading

TypeScript Jump to heading

const name: string = "Alice"
let age: number = 30
const isActive = true // type inference

    

Go Jump to heading

// Explicit type
var name string = "Alice"
var age int = 30

// Type inference (short declaration, most common)
name := "Alice"
age := 30
isActive := true

// Constants
const MaxSize = 100
const (
    StatusOK = 200
    StatusNotFound = 404
)

    

Basic types Jump to heading

TypeScript	Go
string	string
number	int, int8, int16, int32, int64, float32, float64
boolean	bool
any	interface{} or any (Go 1.18+)
null / undefined	Zero values (no null)
Array<T> / T[]	[]T (slice) or [n]T (array)
Record<K, V>	map[K]V

Zero values (instead of null/undefined) Jump to heading

var s string   // ""
var i int      // 0
var b bool     // false
var slice []int // nil (but usable, len=0)

    

Functions Jump to heading

TypeScript Jump to heading

function greet(name: string): string {
    return `Hello, ${name}!`
}

const add = (a: number, b: number): number => a + b

// Optional parameters
function log(message: string, level?: string): void {
    console.log(level ?? "INFO", message)
}

    

Go Jump to heading

// Basic function
func greet(name string) string {
    return "Hello, " + name + "!"
}

// Multiple return values (very common pattern)
func divide(a, b float64) (float64, error) {
    if b == 0 {
        return 0, errors.New("division by zero")
    }
    return a / b, nil
}

// Named return values
func getUser(id int) (user User, found bool) {
    // user and found are pre-declared
    return
}

// Variadic functions (like rest parameters)
func sum(nums ...int) int {
    total := 0
    for _, n := range nums {
        total += n
    }
    return total
}

    

Note: Go has no optional parameters. Use variadic, structs with options, or functional options pattern instead.

Structs (like interfaces/classes) Jump to heading

TypeScript Jump to heading

interface User {
    id: number
    name: string
    email?: string
}

class UserService {
    private users: User[] = []

    addUser(user: User): void {
        this.users.push(user)
    }
}

    

Go Jump to heading

// Struct (like interface + class combined)
type User struct {
    ID    int
    Name  string
    Email string // No optional fields; use pointer for "nullable"
}

// Methods are defined outside the struct
type UserService struct {
    users []User
}

// Method with receiver (like class method)
func (s *UserService) AddUser(user User) {
    s.users = append(s.users, user)
}

// Usage
service := &UserService{}
service.AddUser(User{ID: 1, Name: "Alice"})

    

Interfaces Jump to heading

TypeScript Jump to heading

interface Reader {
    read(buffer: Uint8Array): number
}

interface Writer {
    write(data: Uint8Array): number
}

// Intersection
type ReadWriter = Reader & Writer

    

Go Jump to heading

// Interfaces are implicit (no "implements" keyword)
type Reader interface {
    Read(p []byte) (n int, err error)
}

type Writer interface {
    Write(p []byte) (n int, err error)
}

// Embedding (like intersection)
type ReadWriter interface {
    Reader
    Writer
}

// Any type with these methods automatically implements the interface
type MyFile struct{}

func (f *MyFile) Read(p []byte) (int, error) {
    return 0, nil
}
// MyFile now implements Reader

    

Error handling Jump to heading

TypeScript Jump to heading

try {
    const data = await fetchData()
} catch (error) {
    console.error("Failed:", error)
}

// Or with Result pattern
type Result<T, E> = { ok: true; value: T } | { ok: false; error: E }

    

Go Jump to heading

// Errors are values, not exceptions
result, err := doSomething()
if err != nil {
    return fmt.Errorf("failed to do something: %w", err)
}

// Creating errors
import "errors"

var ErrNotFound = errors.New("not found")

func findUser(id int) (*User, error) {
    if id <= 0 {
        return nil, ErrNotFound
    }
    // ...
    return &user, nil
}

// Error wrapping (like cause chains)
if err != nil {
    return fmt.Errorf("findUser(%d): %w", id, err)
}

// Checking error types
if errors.Is(err, ErrNotFound) {
    // handle not found
}

    

Arrays and slices Jump to heading

TypeScript Jump to heading

const arr: number[] = [1, 2, 3]
arr.push(4)
const doubled = arr.map(n => n * 2)
const evens = arr.filter(n => n % 2 === 0)
const sum = arr.reduce((a, b) => a + b, 0)

    

Go Jump to heading

// Slice (dynamic, like JS array)
arr := []int{1, 2, 3}
arr = append(arr, 4)

// No built-in map/filter/reduce - use loops
doubled := make([]int, len(arr))
for i, n := range arr {
    doubled[i] = n * 2
}

// Filter
var evens []int
for _, n := range arr {
    if n%2 == 0 {
        evens = append(evens, n)
    }
}

// Reduce
sum := 0
for _, n := range arr {
    sum += n
}

// Slicing (same syntax!)
sub := arr[1:3] // [2, 3]

    

Maps (objects/Records) Jump to heading

TypeScript Jump to heading

const scores: Record<string, number> = {
    alice: 100,
    bob: 85
}
scores["charlie"] = 90
const aliceScore = scores["alice"]
delete scores["bob"]

    

Go Jump to heading

// Create map
scores := map[string]int{
    "alice": 100,
    "bob":   85,
}

// Add/update
scores["charlie"] = 90

// Access (returns zero value if missing)
aliceScore := scores["alice"]

// Check if key exists
score, exists := scores["alice"]
if !exists {
    fmt.Println("alice not found")
}

// Delete
delete(scores, "bob")

// Iterate
for name, score := range scores {
    fmt.Printf("%s: %d\n", name, score)
}

    

Concurrency Jump to heading

TypeScript Jump to heading

// Promises and async/await
async function fetchAll(urls: string[]): Promise<Response[]> {
    return Promise.all(urls.map(url => fetch(url)))
}

await fetchAll(["url1", "url2"])

    

Go Jump to heading

// Goroutines (lightweight threads)
go doSomething() // runs concurrently

// Channels (typed pipes for communication)
ch := make(chan string)

go func() {
    ch <- "hello" // send
}()

msg := <-ch // receive

// Buffered channel
ch := make(chan int, 10)

// Select (like Promise.race but for channels)
select {
case msg := <-ch1:
    fmt.Println("from ch1:", msg)
case msg := <-ch2:
    fmt.Println("from ch2:", msg)
case <-time.After(time.Second):
    fmt.Println("timeout")
}

// WaitGroup (like Promise.all)
var wg sync.WaitGroup

for _, url := range urls {
    wg.Add(1)
    go func(u string) {
        defer wg.Done()
        fetch(u)
    }(url)
}

wg.Wait() // blocks until all done

    

Generics (Go 1.18+) Jump to heading

TypeScript Jump to heading

function first<T>(arr: T[]): T | undefined {
    return arr[0]
}

type Stack<T> = {
    items: T[]
    push: (item: T) => void
    pop: () => T | undefined
}

    

Go Jump to heading

// Generic function
func First[T any](slice []T) (T, bool) {
    if len(slice) == 0 {
        var zero T
        return zero, false
    }
    return slice[0], true
}

// Generic type
type Stack[T any] struct {
    items []T
}

func (s *Stack[T]) Push(item T) {
    s.items = append(s.items, item)
}

func (s *Stack[T]) Pop() (T, bool) {
    if len(s.items) == 0 {
        var zero T
        return zero, false
    }
    n := len(s.items) - 1
    item := s.items[n]
    s.items = s.items[:n]
    return item, true
}

// Constraints
type Number interface {
    int | int64 | float64
}

func Sum[T Number](nums []T) T {
    var sum T
    for _, n := range nums {
        sum += n
    }
    return sum
}

    

Package management Jump to heading

TypeScript Jump to heading

npm init
npm install express

    

// package.json
{
    "dependencies": {
        "express": "^4.18.0"
    }
}

    

Go Jump to heading

go mod init myproject
go get github.com/gin-gonic/gin

    

// go.mod
module myproject

go 1.21

require github.com/gin-gonic/gin v1.9.0

    

// Import in code
import "github.com/gin-gonic/gin"

    

JSON handling Jump to heading

TypeScript Jump to heading

interface User {
    id: number
    name: string
    createdAt: Date
}

const json = JSON.stringify(user)
const parsed: User = JSON.parse(json)

    

Go Jump to heading

import "encoding/json"

type User struct {
    ID        int       `json:"id"`
    Name      string    `json:"name"`
    CreatedAt time.Time `json:"createdAt"`
    Password  string    `json:"-"` // Exclude from JSON
    Email     string    `json:"email,omitempty"` // Omit if empty
}

// Marshal (stringify)
data, err := json.Marshal(user)

// Unmarshal (parse)
var user User
err := json.Unmarshal(data, &user)

    

HTTP server Jump to heading

TypeScript (Express) Jump to heading

import express from 'express'

const app = express()
app.use(express.json())

app.get('/users/:id', (req, res) => {
    const id = req.params.id
    res.json({ id, name: 'Alice' })
})

app.listen(3000)

    

Go (standard library) Jump to heading

package main

import (
    "encoding/json"
    "net/http"
)

func main() {
    http.HandleFunc("/users/", func(w http.ResponseWriter, r *http.Request) {
        id := r.URL.Path[len("/users/"):]
        json.NewEncoder(w).Encode(map[string]string{
            "id":   id,
            "name": "Alice",
        })
    })

    http.ListenAndServe(":3000", nil)
}

    

Go (with Gin framework) Jump to heading

import "github.com/gin-gonic/gin"

func main() {
    r := gin.Default()

    r.GET("/users/:id", func(c *gin.Context) {
        id := c.Param("id")
        c.JSON(200, gin.H{"id": id, "name": "Alice"})
    })

    r.Run(":3000")
}

    

Testing Jump to heading

TypeScript (Jest) Jump to heading

describe('math', () => {
    it('adds numbers', () => {
        expect(add(1, 2)).toBe(3)
    })
})

    

Go Jump to heading

// math_test.go (must end in _test.go)
package math

import "testing"

func TestAdd(t *testing.T) {
    result := Add(1, 2)
    if result != 3 {
        t.Errorf("Add(1, 2) = %d; want 3", result)
    }
}

// Table-driven tests (idiomatic Go)
func TestAddTable(t *testing.T) {
    tests := []struct {
        a, b, want int
    }{
        {1, 2, 3},
        {0, 0, 0},
        {-1, 1, 0},
    }

    for _, tt := range tests {
        got := Add(tt.a, tt.b)
        if got != tt.want {
            t.Errorf("Add(%d, %d) = %d; want %d", tt.a, tt.b, got, tt.want)
        }
    }
}

    

go test ./...

    

Common gotchas for TS developers Jump to heading

1. No unused variables/imports - Go won’t compile with unused code
2. Exported names are Capitalized - User is public, user is private
3. No exceptions - use error return values
4. No optional parameters - use variadic or option structs
5. Nil is not null - nil has specific semantics per type
6. Pointers matter - *User vs User affects mutability
7. No ternary operator - use if/else statements
8. Loops only have for - no while, do-while, forEach

Resources Jump to heading

• Go by Example
• A Tour of Go
• Effective Go
• Go Playground
• Go Standard Library

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