Bumped Go version and dependencies

go.mod

@@ -1,19 +1,20 @@
 module github.com/OctopusDeploy/go-octopusdeploy
 
-go 1.12
+go 1.15
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dghubble/sling v1.3.0
 	github.com/go-playground/validator/v10 v10.4.1
 	github.com/google/go-querystring v1.0.0
 	github.com/google/uuid v1.1.2
-	github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a
+	github.com/jinzhu/copier v0.0.0-20201025035756-632e723a6687
 	github.com/kinbiko/jsonassert v1.0.1
 	github.com/kr/text v0.2.0 // indirect
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/stretchr/testify v1.6.1
-	golang.org/x/sys v0.0.0-20190502175342-a43fa875dd82 // indirect
+	golang.org/x/crypto v0.0.0-20201117144127-c1f2f97bffc9 // indirect
+	golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 // indirect
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 	gopkg.in/yaml.v3 v3.0.0-20200615113413-eeeca48fe776 // indirect
 )