Update Dockerfile to use Go v1.21 (#455)

Signed-off-by: goodfirm <fanyishang@yeah.net>

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.18-alpine as builder
+FROM golang:1.21-alpine as builder
 MAINTAINER Fullstory Engineering
 
 # create non-privileged group and user

cmd/grpcurl/grpcurl.go

@@ -33,9 +33,9 @@ import (
 	"github.com/fullstorydev/grpcurl"
 )
 
-// To avoid confusion between program error codes and the gRPC resonse
+// To avoid confusion between program error codes and the gRPC response
 // status codes 'Cancelled' and 'Unknown', 1 and 2 respectively,
-// the response status codes emitted use an offest of 64
+// the response status codes emitted use an offset of 64
 const statusCodeOffset = 64
 
 const noVersion = "dev build <no version set>"