Go🔧Core Languagebeginner

Control Flow

Go · Core Language · Run with go run

Explanation

Go has `if`, `for`, and `switch` — no `while`, no `do-while`, no `until`. `for` covers all looping: classic C-style, while-style, and range-based. `switch` does not fall through by default (no `break` needed); use `fallthrough` explicitly when required.

Real-World Scenario

`for range` over a channel is the standard way to consume a stream of results from a concurrent worker, blocking until the channel is closed.

Quick Snippet

snippet.go

// if with initialization statement
if err := doWork(); err != nil {
    log.Fatal(err)
}

// for as while
for running {
    process()
}

// range over slice (index, value)
for i, v := range items {
    fmt.Println(i, v)
}

// switch — no fall-through by default
switch status {
case 200: fmt.Println("OK")
case 404: fmt.Println("Not Found")
default:  fmt.Println("Other")
}

Full Example

View on GitHub

control_flow.go

// Compile: go run control_flow.go
// Output:
//   err check: ok
//   countdown: 3 2 1
//   even: 0 2 4
//   status 200: OK
package main

import "fmt"

func doWork() error { return nil }

func main() {
	// if with initialization statement
	if err := doWork(); err != nil {
		fmt.Println("error:", err)
	} else {
		fmt.Println("err check: ok")
	}

	// for as while
	n := 3
	fmt.Print("countdown:")
	for n > 0 {
		fmt.Print(" ", n)
		n--
	}
	fmt.Println()

	// range over slice
	fmt.Print("even:")
	for _, v := range []int{0, 1, 2, 3, 4} {
		if v%2 != 0 {
			continue
		}
		fmt.Print(" ", v)
	}
	fmt.Println()

	// switch — no fall-through by default
	status := 200
	switch status {
	case 200:
		fmt.Println("status 200: OK")
	case 404:
		fmt.Println("status 404: Not Found")
	default:
		fmt.Println("status: Other")
	}
}

Run command

bash

go run control_flow.go

Functions

Structs