Time to update to Go Mod 1.15?

[salaboy]

I was building the provider image with the provided Dockerfile and I was getting this error:

 => ERROR [builder 9/9] RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on go build -a -o provider cmd/provider/main.go                                                                       26.6s
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 > [builder 9/9] RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on go build -a -o provider cmd/provider/main.go:
#17 26.34 # sigs.k8s.io/controller-runtime/pkg/manager
#17 26.34 /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.8.0/pkg/manager/manager.go:53:2: duplicate method Start
#17 26.34 note: module requires Go 1.15

I've tried upgrading to Go Mod 1.15 and it works.. so I will send a PR with the changes I made.. but someone needs to validate that something else is not broken because of that..