String is a read-only slice of bytes. Strings are immutable in Go means once you created you can't modify the contents of a string. When you define a string with characters, you are actually storing it's bytes not the characters.

How to declare strings

Syntax

var string-name = value;

For example, you can define a string variable like below:

var str = "OneCompiler";

Example

package main  
import ("fmt"  
      "reflect"  
)  
func main()  {  
   var str = "One Compiler"  
   fmt.Println(str)  
   fmt.Println(reflect.TypeOf(str))  
   
   fmt.Printf("Quoted string is: ")
   for i := 0; i < len(str); i++ {
    fmt.Printf("%+q", str[i])
   }
  
   fmt.Printf("\n")
   fmt.Printf("Hex bytes of the string is: ")
   for i := 0; i < len(str); i++ {
      fmt.Printf("%x ", str[i])
   }
   fmt.Printf("\n")
} 

Check result here

String Functions

Go has various in-built string functions which can manipulate strings. Below are some of the frequently used string functions.

Function name	Description
len(str)	to return the length of string str
strings.Compare(a, b)	Compares two strings a and b lexically and returns 0 if the both strings are equal and 1 if string 1 is greater than string 2 and -1 if string 1 is less than string 2.
strings.Contains(str, substr)	returns true if substring is found in the string str
strings.ToUpper(str)	to change the str to Upper Case
strings.ToLower(str)	to change the str to lower Case
strings.HasPrefix(str,"prefix")	returns true if the string str is starting with a prefix
strings.HasSuffix(str,"suffix")	returns true if the string str is ending with a suffix
strings.Index(str, substr)	searches for a particular text within a string and returns it's index. If not found then it will returns -1.
strings.Join(stringSlice []string, sep string)	contanates the elements of an slice with seperators
strings.Count(str, sep string)	returns the count of number of non-overlapping instances of a character/string/text in string

Examples

package main
import "fmt"
import "strings"

func main() {
   var str =  "Good morning!"
   
  // String Length
   fmt.Println("Length of the str is:", len(str))  
   
  // string compare
  fmt.Println("\nComparing Strings:")
  fmt.Println(strings.Compare("Apple", "Banana"))
  fmt.Println(strings.Compare("Banana", "Apple"))
  fmt.Println(strings.Compare("Apple", "Apple"))
  
  // string contains
  fmt.Println("\nWhether String contains?")
  fmt.Println(strings.Contains("Apple", "A")) 
  fmt.Println(strings.Contains("Apple", "Ba")) 
  
  //Uppercase and Lowercase
  fmt.Println("\nChanging Case")
  fmt.Println(strings.ToUpper("Hello world!"))
  fmt.Println(strings.ToLower("happy learning!!"))
 
  // string prefix and suffix checking
  fmt.Println("\nChecking Prefix and suffix:")
  fmt.Println(strings.HasPrefix("Hello World", "Hello"))
  fmt.Println(strings.HasPrefix("Hello World", "hello"))
  fmt.Println(strings.HasSuffix("Hello World", "World"))
  
  //String Index
  fmt.Println("\nFinding Index:")
  fmt.Println(strings.Index("Hello World", "World"))
  
  //String Join
  fmt.Println("\nUsing String Join:")
  sampleSlice := []string{"one", "two", "three", "four", "five"}
  fmt.Println(strings.Join(sampleSlice,"*"))
  
  // String count
  fmt.Println("\nCount:")
  fmt.Println(strings.Count("Hello World", "World"))
  fmt.Println(strings.Count("Hello World", "l"))
  
}

Check result here