Fixed lint issues and missing documentation

internal/mock/findATender/ratelimit.go

@@ -11,6 +11,7 @@ import (
 
 // ---------- rate limiting ----------
 
+// clientWindow is one client's rate limiting state.
 type clientWindow struct {
 	hour        time.Time // clock hour the anchor belongs to
 	anchor      time.Time // first request of that hour
@@ -18,6 +19,10 @@ type clientWindow struct {
 	count       int       // accepted requests in the current window
 }
 
+// RateLimiter limits each client (by remote host) to a number of requests per
+// fixed window, answering the rest with 429 Too Many Requests and a
+// Retry-After header, as the Find a Tender API does. A client's windows are
+// counted from its first request in each clock hour.
 type RateLimiter struct {
 	mu      sync.Mutex
 	limit   int
@@ -26,6 +31,7 @@ type RateLimiter struct {
 	now     func() time.Time
 }
 
+// NewRateLimiter returns a RateLimiter allowing limit requests per window.
 func NewRateLimiter(limit int, window time.Duration) *RateLimiter {
 	return &RateLimiter{
 		limit:   limit,
@@ -108,7 +114,7 @@ func (rl *RateLimiter) Middleware(next http.HandlerFunc) http.HandlerFunc {
 			w.Header().Set("Retry-After", strconv.Itoa(retry))
 			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 			w.WriteHeader(http.StatusTooManyRequests)
-			fmt.Fprintf(
+			_, _ = fmt.Fprintf(
 				w, "Rate limit of %d exceeded. Please retry after %d seconds.",
 				rl.limit, retry,
 			)