Best way to time upstream requests in Golang?

Is there a good way to time how long it takes for each upstream server that my http server is connecting to, without sprinkling time.Now and time.Since everywhere?

Is your main concern performance? You're tracking a network request so I don't think fetching for the latest time is going to impact your performance at all. If you can gather performance data that shows you're dying from making calls to get the current time, you could build a clock that ticks every 10ms or whatever to give you a "good enough" approximation of the request time. But again, benchmark with and without time. I seriously doubt you'll see a difference. 

Well, I am trying to see which request that takes the longest time. If you have a service that talks to multiple different things in a single call, I need to know which one of these that's taking the longest.

Create a new request type that embeds an http.Request, and wrap the methods you want to time.