Why modifying a String in Go is NOT allocating extra space?

I'm new to Go and trying to understand how Strings work in Go. My major doubt is, why changing str from "black" to "Orange" in my example NOT change the address of str. I notice the address changes while making a copy with str_cpy.

Thanks in advance.

Code:

func main(){
  // set str as Black
  var str string = "Black"
  log.Println("String is set to: ", str)
  log.Println("Current address of String is: ", &str)

  //set str as black
  log.Println("Testing Mutability...")
  slice := []rune(str)
  slice[0] = 'b'
  str = string(slice)
  log.Println("String after mutation is...", str)
  log.Println("Current address of String is: ", &str)
 
  //make a copy of str, str_cpy expected value: black
  str_cpy := str
  log.Println("StringCOPY is set to: ", str_cpy)
  log.Println("Current address of StringCOPY is: ", &str_cpy)

  //change str from black to Orange
  str = "Orange"
  log.Println("String now is...", str)
  log.Println("Current address of String is: ", &str)

  changeusingPointer(&str)
  log.Println("String was changed using pointer to: ", str)
  log.Println("Current address of String is: ", &str)
  
}

func changeusingPointer(s *string){
  log.Println("s points to ", s)
  *s = "White"
}

The Output I get is:

2023/02/18 10:39:38 String is set to:  Black
2023/02/18 10:39:38 Current address of String is:  0xc000014060
2023/02/18 10:39:38 Testing Mutability...
2023/02/18 10:39:38 String after mutation is... black
2023/02/18 10:39:38 Current address of String is:  0xc000014060
2023/02/18 10:39:38 StringCOPY is set to:  black
2023/02/18 10:39:38 Current address of StringCOPY is:  0xc000014090
2023/02/18 10:39:38 String now is... Orange
2023/02/18 10:39:38 Current address of String is:  0xc000014060
2023/02/18 10:39:38 s points to  0xc000014060
2023/02/18 10:39:38 String was changed using pointer to:  White
2023/02/18 10:39:38 Current address of String is:  0xc000014060

I expected the address of string str to change while changing its value from "black" to "Orange" .

A string is a structure containing two elements: pointer to the array containing the string, and the string length. So when you declare str="Orange", what happens resembles the following:

str=internalString{ arr: <pointer to array "Orange">, len: 6}

When you assign a new value to str, like "Black", this becomes:

str=internalString{ arr: <pointer to array "Black">, len: 5}

Address of str does not change.

when you create str_copy you copy the value and put it some where else so the pointer should change but when you change the value of str the array pointer remains constant just the values change