GoHow-ToBeginner · 3 min read

How to Take Input in Go: Simple Guide with Examples

In Go, you can take input from the user using fmt.Scan, fmt.Scanln, or bufio.Reader. The fmt.Scan functions read input from the standard input (keyboard) and store it in variables.

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Syntax

To take input in Go, you commonly use the fmt.Scan or fmt.Scanln functions. They read input from the keyboard and store it in variables passed by reference.

fmt.Scan(&variable): Reads input separated by spaces.
fmt.Scanln(&variable): Reads input until a newline.
bufio.NewReader(os.Stdin): For reading full lines or more complex input.

var name string
fmt.Scan(&name) // reads a word

var age int
fmt.Scanln(&age) // reads an integer until newline

reader := bufio.NewReader(os.Stdin)
line, _ := reader.ReadString('\n') // reads a full line including spaces

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Example

This example shows how to take a user's name and age as input and then print a greeting message.

package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

func main() {
	var name string
	var age int

	fmt.Print("Enter your name: ")
	fmt.Scanln(&name)

	fmt.Print("Enter your age: ")
	fmt.Scan(&age)

	reader := bufio.NewReader(os.Stdin)
	fmt.Print("Enter your favorite quote: ")
	quote, _ := reader.ReadString('\n')
	quote = strings.TrimSpace(quote)

	fmt.Printf("Hello %s, you are %d years old.\n", name, age)
	fmt.Printf("Your favorite quote is: %s\n", quote)
}

Output

Enter your name: Alice Enter your age: 30 Enter your favorite quote: Go is awesome! Hello Alice, you are 30 years old. Your favorite quote is: Go is awesome!

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Common Pitfalls

Common mistakes when taking input in Go include:

Not using the address operator & when passing variables to fmt.Scan or fmt.Scanln.
Mixing fmt.Scan and bufio.Reader without clearing the input buffer, which can cause unexpected behavior.
Assuming fmt.Scan reads the whole line; it stops at spaces.

Always handle errors returned by input functions for robust code.

package main

import (
	"fmt"
)

func main() {
	var name string

	// Wrong: missing & operator
	// fmt.Scanln(name) // This will cause a compile error

	// Right:
	fmt.Scanln(&name)

	fmt.Printf("Hello %s\n", name)
}

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Quick Reference

Here is a quick summary of input functions in Go:

Function	Description	Notes
fmt.Scan(&vars)	Reads space-separated values from stdin	Stops at space, requires &
fmt.Scanln(&vars)	Reads input until newline	Stops at newline, requires &
bufio.Reader.ReadString('\n')	Reads full line including spaces	Returns string with newline, trim if needed
bufio.Reader.ReadBytes('\n')	Reads bytes until newline	Useful for binary or raw input

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Key Takeaways

Use fmt.Scan or fmt.Scanln with &variable to read input from the keyboard.

bufio.Reader is useful for reading full lines or complex input with spaces.

Always pass variables by reference using & when scanning input.

Handle input errors and be aware of how input functions treat spaces and newlines.

Mixing fmt.Scan and bufio.Reader requires care to avoid leftover input issues.