start GRPCWebServer in goroutine

so it don't block other code from executing.

Closes cosmos#9703

server/grpc/grpc_web.go

@@ -1,7 +1,9 @@
 package grpc
 
 import (
+	"fmt"
 	"net/http"
+	"time"
 
 	"github.com/improbable-eng/grpc-web/go/grpcweb"
 	"google.golang.org/grpc"
@@ -28,8 +30,16 @@ func StartGRPCWeb(grpcSrv *grpc.Server, config config.Config) (*http.Server, err
 		Addr:    config.GRPCWeb.Address,
 		Handler: http.HandlerFunc(handler),
 	}
-	if err := grpcWebSrv.ListenAndServe(); err != nil {
+	errCh := make(chan error)
+	go func() {
+		if err := grpcWebSrv.ListenAndServe(); err != nil {
+			errCh <- fmt.Errorf("failed to serve: %w", err)
+		}
+	}()
+	select {
+	case err := <-errCh:
 		return nil, err
+	case <-time.After(5 * time.Second): // assume server started successfully
+		return grpcWebSrv, nil
 	}
-	return grpcWebSrv, nil
 }