What does the ampersand (&) before http.Client{} mean?

An ampersand (&) before the expression http.Client{} in Go indicates taking the address (pointer) of the created http.Client struct object. That is, &http.Client{} creates a new instance of the struct and returns a pointer to it.

This is useful when you need to pass a reference to the object to avoid copying the struct or to be able to modify the object through the pointer.

Example:

client := &http.Client{}
// client has type *http.Client

Without the ampersand, the variable will contain the struct itself, not a pointer to it.