fmt.Println() / Print() / Printf()

import "fmt"

// Prints with a newline (spaces are added between arguments).
fmt.Println(value1, value2, ...)

// Prints without spaces (spaces are added between non-string adjacent arguments).
fmt.Print(value1, value2, ...)

// Prints using a format string.
fmt.Printf("format string", value1, value2, ...)

package main

import "fmt"

type Point struct {
    X, Y int
}

func main() {
    name := "Go"
    version := 1.22
    year := 2024

    // Println: adds spaces between arguments and a newline at the end.
    fmt.Println("Hello, World!")
    fmt.Println(name, "version", version)
    fmt.Println("Release year:", year)

    fmt.Println()

    // Print: no newline. Adds spaces between adjacent non-string arguments.
    fmt.Print("A")
    fmt.Print("B")
    fmt.Print("C\n") // Add a newline manually.
    fmt.Print(1, 2, 3, "\n")   // Spaces are added between numbers.
    fmt.Print("x", "y", "\n") // No spaces between strings.

    fmt.Println()

    // Printf: prints using format verbs.
    fmt.Printf("Language: %s\n", name)
    fmt.Printf("Version: %.2f\n", version)
    fmt.Printf("Decimal: %d, Octal: %o, Hex: %x\n", 255, 255, 255)
    fmt.Printf("Boolean: %t\n", true)
    fmt.Printf("Pointer: %p\n", &year)

    // Printing a struct
    p := Point{X: 10, Y: 20}
    fmt.Printf("Value: %v\n", p)          // Default format
    fmt.Printf("With field names: %+v\n", p) // With field names
    fmt.Printf("Go syntax: %#v\n", p)     // Go syntax representation
    fmt.Printf("Type: %T\n", p)           // Type name
}

Use fmt.Println() for debugging and simple output, and fmt.Printf() for formatting numbers and strings. For a full list of format verbs (such as %v and %d), see Format Verbs. To format a value as a string instead of printing it, use fmt.Sprintf().

If the number of format verbs and arguments do not match in fmt.Printf(), no compile error occurs — instead, the output will contain %!(EXTRA ...) or %!(MISSING ...) at runtime. Use the go vet command to detect these mistakes.

For string formatting, see fmt.Sprintf() / fmt.Fprintf(). For reading from standard input, see fmt.Scan().