go - Immutable string and pointer address

Question

In Go spec is written:

Strings are immutable: once created, it is impossible to change the contents of a string.

I have following code:

str := "hello"
fmt.Printf("%p
",&str) // 0x1040c128
fmt.Printf("%v
",str) // hello
ptr := &str
*ptr = "world"
fmt.Printf("%p
",&str) // 0x1040c128
fmt.Printf("%v
",str) // world  

I would have expected &str address was changed after *ptr = "world". As it would happen with Java, where we reassign String references.

What is 'immutability' here?

Answer 1

Waitting for answers