assert trailing slash for handler prefixes

pkg/srv/http/http.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -60,6 +61,13 @@ func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
 	// Inject extra handlers if given
 	// Used for grpc-gateway runtime.ServeMux handlers
 	for _, h := range opts.Handlers {
+		// prefix must end in / to route sub-paths
+		if !strings.HasSuffix(h.Prefix, "/") {
+			h.Prefix = h.Prefix + "/"
+		}
+
+		// if enabled, the path prefix is stripped before
+		// requests are sent to the handler
 		if h.StripPrefix {
 			h.Handler = http.StripPrefix(h.Prefix, h.Handler)
 		}