Update to Go 1.21

Signed-off-by: Artur Souza <asouza.pro@gmail.com>

go.mod

@@ -1,6 +1,8 @@
 module github.com/diagridio/go-etcd-cron
 
-go 1.20
+go 1.21
+
+toolchain go1.21.8
 
 require (
 	github.com/pkg/errors v0.9.1

go.sum

@@ -10,6 +10,7 @@ github.com/gogo/protobuf v1.3.2/go.mod h1:P1XiOD3dCwIKUDQYPy72D8LYyHL2YPYrpS2s69
 github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
@@ -29,6 +30,7 @@ go.etcd.io/etcd/client/pkg/v3 v3.5.12/go.mod h1:seTzl2d9APP8R5Y2hFL3NVlD6qC/dOT+
 go.etcd.io/etcd/client/v3 v3.5.12 h1:v5lCPXn1pf1Uu3M4laUE2hp/geOTc5uPcYYsNe1lDxg=
 go.etcd.io/etcd/client/v3 v3.5.12/go.mod h1:tSbBCakoWmmddL+BKVAJHa9km+O/E+bumDe9mSbPiqw=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
+go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 go.uber.org/multierr v1.11.0 h1:blXXJkSxSSfBVBlC76pxqeO+LN3aDfLQo+309xJstO0=
 go.uber.org/multierr v1.11.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
 go.uber.org/zap v1.27.0 h1:aJMhYGrd5QSmlpLMr2MftRKl7t8J8PTZPA732ud/XR8=