Fix broken syntax, incorrect parameter types, etc in examples

RateLimiting.md

@@ -8,8 +8,8 @@ For higher rates, prefer a token bucket rate limiter (search godoc.org for
 ```go
 import "time"
 
-ratePerSec := 10
-throttle := time.Tick(1e9 / ratePerSec)
+rate := time.Second / 10
+throttle := time.Tick(rate)
 for req := range requests {
   <-throttle  // rate limit our Service.Method RPCs
   go client.Call("Service.Method", req, ...)
@@ -20,15 +20,15 @@ To allow some bursts, add a buffer to the throttle:
 ```go
 import "time"
 
-ratePerSec := 10
+rate := time.Second / 10
 burstLimit := 100
-tick := time.NewTicker(1e9 / ratePerSec)
+tick := time.NewTicker(rate)
 defer tick.Stop()
 throttle := make(chan time.Time, burstLimit)
 go func() {
-  for t := range tick {
+  for t := range tick.C {
     select {
-      case: throttle <- t
+      case throttle <- t:
       default:
     }
   }  // exits after tick.Stop()