Merge pull request #9 from moul/renovate/docker-all

chore(deps): update golang docker tag to v1.15.5

Dockerfile

@@ -4,7 +4,7 @@ ARG             VCS_REF
 ARG             VERSION
 
 # build
-FROM            golang:1.15.4-alpine as builder
+FROM            golang:1.15.5-alpine as builder
 RUN             apk add --no-cache git gcc musl-dev make
 ENV             GO111MODULE=on
 WORKDIR         /go/src/moul.io/berty-library-test