Bumped terraform and golang versions

Updated terraform to 0.12.29
and Golang to 1.15

Dockerfile

@@ -1,5 +1,5 @@
 # Fetch the dependencies
-FROM golang:1.12-alpine AS builder
+FROM golang:1.15-alpine AS builder
 
 RUN apk add --update ca-certificates git gcc g++ libc-dev
 WORKDIR /src/
@@ -18,6 +18,6 @@ RUN CGO_ENABLED=0 GOOS=linux go build
 
 
 # Build the final image
-FROM hashicorp/terraform:0.11.14
+FROM hashicorp/terraform:0.12.29
 
 COPY --from=builder /src/terraform-provider-artifactory /root/.terraform.d/plugins/

go.mod

@@ -2,8 +2,8 @@ module github.com/atlassian/terraform-provider-artifactory
 
 require (
 	github.com/atlassian/go-artifactory/v2 v2.5.0
-	github.com/hashicorp/terraform v0.12.0
-	github.com/stretchr/testify v1.3.0
+	github.com/hashicorp/terraform v0.12.29
+	github.com/stretchr/testify v1.5.1
 )
 
-go 1.13
+go 1.15