Update plugin-go to 0.2.1.

Contains some bug fixes we want, like a fix for panics when calling
Stop.

go.mod

@@ -27,7 +27,7 @@ require (
 	github.com/hashicorp/logutils v1.0.0
 	github.com/hashicorp/terraform-exec v0.12.0
 	github.com/hashicorp/terraform-json v0.8.0
-	github.com/hashicorp/terraform-plugin-go v0.1.0
+	github.com/hashicorp/terraform-plugin-go v0.2.1
 	github.com/hashicorp/yamux v0.0.0-20181012175058-2f1d1f20f75d // indirect
 	github.com/keybase/go-crypto v0.0.0-20161004153544-93f5b35093ba
 	github.com/kylelemons/godebug v1.1.0 // indirect

go.sum

@@ -173,8 +173,6 @@ github.com/hashicorp/go-getter v1.4.0/go.mod h1:7qxyCd8rBfcShwsvxgIguu4KbS3l8bUC
 github.com/hashicorp/go-getter v1.5.0 h1:ciWJaeZWSMbc5OiLMpKp40MKFPqO44i0h3uyfXPBkkk=
 github.com/hashicorp/go-getter v1.5.0/go.mod h1:a7z7NPPfNQpJWcn4rSWFtdrSldqLdLPEF3d8nFMsSLM=
 github.com/hashicorp/go-hclog v0.0.0-20180709165350-ff2cf002a8dd/go.mod h1:9bjs9uLqI8l75knNv3lV1kA55veR+WUPSiKIWcQHudI=
-github.com/hashicorp/go-hclog v0.9.2 h1:CG6TE5H9/JXsFWJCfoIVpKFIkFe6ysEuHirp4DxCsHI=
-github.com/hashicorp/go-hclog v0.9.2/go.mod h1:5CU+agLiy3J7N7QjHK5d05KxGsuXiQLrjA0H7acj2lQ=
 github.com/hashicorp/go-hclog v0.14.1 h1:nQcJDQwIAGnmoUWp8ubocEX40cCml/17YkF6csQLReU=
 github.com/hashicorp/go-hclog v0.14.1/go.mod h1:whpDNt7SSdeAju8AWKIWsul05p54N/39EeqMAyrmvFQ=
 github.com/hashicorp/go-hclog v0.15.0 h1:qMuK0wxsoW4D0ddCCYwPSTm4KQv1X1ke3WmPWZ0Mvsk=
@@ -204,8 +202,8 @@ github.com/hashicorp/terraform-exec v0.12.0 h1:Tb1VC2gqArl9EJziJjoazep2MyxMk00tn
 github.com/hashicorp/terraform-exec v0.12.0/go.mod h1:SGhto91bVRlgXQWcJ5znSz+29UZIa8kpBbkGwQ+g9E8=
 github.com/hashicorp/terraform-json v0.8.0 h1:XObQ3PgqU52YLQKEaJ08QtUshAfN3yu4u8ebSW0vztc=
 github.com/hashicorp/terraform-json v0.8.0/go.mod h1:3defM4kkMfttwiE7VakJDwCd4R+umhSQnvJwORXbprE=
-github.com/hashicorp/terraform-plugin-go v0.1.0 h1:kyXZ0nkHxiRev/q18N40IbRRk4AV0zE/MDJkDM3u8dY=
-github.com/hashicorp/terraform-plugin-go v0.1.0/go.mod h1:10V6F3taeDWVAoLlkmArKttR3IULlRWFAGtQIQTIDr4=
+github.com/hashicorp/terraform-plugin-go v0.2.1 h1:EW/R8bB2Zbkjmugzsy1d27yS8/0454b3MtYHkzOknqA=
+github.com/hashicorp/terraform-plugin-go v0.2.1/go.mod h1:10V6F3taeDWVAoLlkmArKttR3IULlRWFAGtQIQTIDr4=
 github.com/hashicorp/yamux v0.0.0-20180604194846-3520598351bb/go.mod h1:+NfK9FKeTrX5uv1uIXGdwYDTeHna2qgaIlx54MXqjAM=
 github.com/hashicorp/yamux v0.0.0-20181012175058-2f1d1f20f75d h1:kJCB4vdITiW1eC1vq2e6IsrXKrZit1bv/TDYFGMp4BQ=
 github.com/hashicorp/yamux v0.0.0-20181012175058-2f1d1f20f75d/go.mod h1:+NfK9FKeTrX5uv1uIXGdwYDTeHna2qgaIlx54MXqjAM=