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How to check if a string contains only letters in Golang?

Checking if a string contains letters returns True if the string contains all letters, and False otherwise. Letters include any alphabetic character and excludes digits, punctuation, and other special characters.

Example using unicode.IsLetter function 
package main

import (
	"fmt"
	"unicode"
)

func IsLetter(s string) bool {
	for _, r := range s {
		if !unicode.IsLetter(r) {
			return false
		}
	}
	return true
}

func main() {
	fmt.Println(IsLetter("Golang")) // true
	fmt.Println(IsLetter("Golang#54"))  // false
}
Example using strings.Contains function 
package main

import (
	"fmt"
	"strings"
)

const alpha = "abcdefghijklmnopqrstuvwxyz"

func alphaOnly(s string) bool {
	for _, char := range s {
		if !strings.Contains(alpha, strings.ToLower(string(char))) {
			return false
		}
	}
	return true
}

func main() {
	fmt.Println(alphaOnly("Golang"))    // true
	fmt.Println(alphaOnly("Golang#54")) // false
}
Example using Regex 
package main

import (
	"fmt"
	"regexp"
)

var IsLetter = regexp.MustCompile(`^[a-zA-Z]+$`).MatchString

func main() {
	fmt.Println(IsLetter("Golang"))    // true
	fmt.Println(IsLetter("Golang#54")) // false
}
Regular expression is widely used for pattern matching. The regexp package provides support for regular expressions, which allow complex patterns to be found in strings. The regexp.MustCompile() function is used to create the regular expression and the MatchString() function returns a bool that indicates whether a pattern is matched by the string.
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