Golang passing a variable by reference to a structure member value

Question

I am having difficulties passing a value to a struct by reference or by passing a pointer. I will outline what I am trying to achieve:

type FooStruct struct {
    foo1, foo2, foo3 int //etc
    connection *net.Conn
}

func(session FooStruct) Run(conn *net.Conn) {
    session.connection = conn
    session.connection.RemoteAddr()
    ......
}

func main() {
    server, err := net.Listen("tcp", ":8484")
    connection, err := server.Accept()
    foo := FooStruct{}
    foo.Run(&connection)
}

The above is an example of what I am trying to achive I only want to pass a reference pointer to the connection variable in the struct. I have tried reading the documentation and going through the tutorial but I have become confused.

When compiling I get the error - session.connection.RemoteAddr undefined (type * net.Conn has no field or method RemoteAddr). It does have that method as when copying the variable it works fine. However that is not what I want to do.

Solution

Since net.Conn is an interface, not a struct, you should pass and store it directly. Like this:

type FooStruct struct {
    foo1, foo2, foo3 int
    connection       net.Conn
}

func(session *FooStruct) Run(conn net.Conn) {
    session.connection = conn
    session.connection.RemoteAddr()
}

func main() {
    server, err := net.Listen("tcp", ":8484")
    connection, err := server.Accept()
    foo := FooStruct{}
    foo.Run(connection)
}

See also the Go FAQ entry on passing interfaces to pointers.

Also note that I changed the receiver of the Run method to a pointer, which is generally what you want.