switch to golang 1.21

Signed-off-by: Markus Blaschke <mblaschke82@gmail.com>

Dockerfile

@@ -1,7 +1,7 @@
 #############################################
 # Build
 #############################################
-FROM --platform=$BUILDPLATFORM golang:1.20-alpine as build
+FROM --platform=$BUILDPLATFORM golang:1.21-alpine as build
 
 RUN apk upgrade --no-cache --force
 RUN apk add --update build-base make git

go.mod

@@ -1,6 +1,6 @@
 module github.com/webdevops/go-crond
 
-go 1.20
+go 1.21
 
 require (
 	github.com/jessevdk/go-flags v1.5.0

go.sum

@@ -8,6 +8,7 @@ github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/jessevdk/go-flags v1.5.0 h1:1jKYvbxEjfUl0fmqTCOfonvskHHXMjBySTLW4y9LFvc=
 github.com/jessevdk/go-flags v1.5.0/go.mod h1:Fw0T6WPc1dYxT4mKEZRfG5kJhaTDP9pj1c2EWnYs/m4=
 github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 h1:jWpvCLoY8Z/e3VKvlsiIGKtc+UG6U5vzxaoagmhXfyg=