fix: go up version to 1.21

go.mod

@@ -1,17 +1,17 @@
 module restic-exporter
 
-go 1.17
+go 1.21
 
-require github.com/prometheus/client_golang v1.12.2
+require github.com/prometheus/client_golang v1.17.0
 
 require (
 	github.com/beorn7/perks v1.0.1 // indirect
-	github.com/cespare/xxhash/v2 v2.1.2 // indirect
-	github.com/golang/protobuf v1.5.2 // indirect
-	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
-	github.com/prometheus/client_model v0.2.0 // indirect
-	github.com/prometheus/common v0.32.1 // indirect
-	github.com/prometheus/procfs v0.7.3 // indirect
-	golang.org/x/sys v0.0.0-20220114195835-da31bd327af9 // indirect
-	google.golang.org/protobuf v1.26.0 // indirect
+	github.com/cespare/xxhash/v2 v2.2.0 // indirect
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
+	github.com/prometheus/client_model v0.4.1-0.20230718164431-9a2bf3000d16 // indirect
+	github.com/prometheus/common v0.44.0 // indirect
+	github.com/prometheus/procfs v0.11.1 // indirect
+	golang.org/x/sys v0.11.0 // indirect
+	google.golang.org/protobuf v1.31.0 // indirect
 )