fix(deps): update module github.com/slack-go/slack to v0.8.1

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/json-iterator/go v1.1.10
 	github.com/magefile/mage v1.11.0
 	github.com/pelletier/go-toml v1.6.0 // indirect
-	github.com/slack-go/slack v0.8.0
+	github.com/slack-go/slack v0.8.1
 	github.com/spf13/afero v1.2.2 // indirect
 	github.com/spf13/cast v1.3.1 // indirect
 	github.com/spf13/cobra v1.0.0

go.sum

@@ -221,8 +221,8 @@ github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
 github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
-github.com/slack-go/slack v0.8.0 h1:ANyLY5KHLV+MxLJDQum2IuHTLwbCbDtaWY405X1EU9U=
-github.com/slack-go/slack v0.8.0/go.mod h1:FGqNzJBmxIsZURAxh2a8D21AnOVvvXZvGligs4npPUM=
+github.com/slack-go/slack v0.8.1 h1:NqGXuzni8Is3EJWmsuMuBiCCPbWOlBgTKPvdlwS3Huk=
+github.com/slack-go/slack v0.8.1/go.mod h1:FGqNzJBmxIsZURAxh2a8D21AnOVvvXZvGligs4npPUM=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d h1:zE9ykElWQ6/NYmHa3jpm/yHnI4xSofP+UP6SpjHcSeM=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
 github.com/smartystreets/goconvey v1.6.4 h1:fv0U8FUIMPNf1L9lnHLvLhgicrIVChEkdzIKYqbNC9s=