Golang: How to convert int to calculate into time.duration

I'm new to GoLang and at the moment at a loss why the compiler does not accept a particular line of code.

I've got this working example for creating a timeout when dialing:

    conn, err := grpc.Dial(*connAddress,
	  grpc.WithInsecure(),
	  grpc.WithBlock(),                  // will block till the connection is available
	  grpc.WithTimeout(100*time.Second)) // times out after 100 seconds

Now the hardcoded 100 there is not nice, so I would like to make that a commandline variable via a flag, like so:

    connTimeout := flag.Int64("connection-timeout", 100, "give the timeout for dialing connection x")
...
    conn, err := grpc.Dial(*connAddress,
	  grpc.WithInsecure(),
	  grpc.WithBlock(),
	  grpc.WithTimeout(*connTimeout*time.Second)) 

However this gives the following compilation error:

> mismatched types int64 and time.Duration

So apparently I can't use the int64 flag variable directly to calculate a duration but a number can?

Eventually I found a solution for using the flag variable by creating a variable related to time.Duration first:

var timeoutduration = time.Duration(*distributorTimeout) * time.Second
	// create distributor connection
	conn, err := grpc.Dial(*connAddress,
		grpc.WithBlock(),
		grpc.WithTimeout(timeoutduration)) 

The above seems to work as expected: the dialing is tried for as long as the commandline parameter given (default 100) and than throws a message that the connection could not be made. Good.

However: How come directly using the int64 flag-variable is not possible for calculating a time.Duration, in other words what is the difference for golang between the number 100 and the variable that contains the int64?

grpc.WithTimeout(100*time.Second) and grpc.WithTimeout(*connTimeout*time.Second) does not because of assignability rules:

the latter expression satisfies none of those, and the former satisfies the

• x is an untyped constant representable by a value of type T.

rule