Update to go v1.12.1

Dockerfile.dapper

-FROM golang:1.11.4-alpine3.8
-# FROM arm=golang@sha256:fe81149b4e7f07ecb558fd16cdbcdb11e739846a046e38cc6e170aa39a67e7ec arm64=golang@sha256:da9c2d140ed4bf911ef8f6d9437912b80497c256ef2235c65836eac83d1c0ce7
+FROM golang:1.12.1-alpine3.9
 
 RUN apk -U --no-cache add bash git gcc musl-dev docker vim less file curl wget ca-certificates jq linux-headers zlib-dev tar zip squashfs-tools npm coreutils \
     python3 py3-pip python3-dev openssl-dev libffi-dev libseccomp libseccomp-dev make
@@ -7,7 +6,7 @@ RUN pip3 install 'tox==3.6.0'
 RUN apk -U --no-cache --repository http://dl-3.alpinelinux.org/alpine/edge/main/ add sqlite-dev sqlite-static
 RUN mkdir -p /go/src/golang.org/x && \
     cd /go/src/golang.org/x && git clone https://github.com/golang/tools && \
-    git -C /go/src/golang.org/x/tools checkout -b current e9f45831faab4562ce3f53f7196b67c08f948e86 && \
+    git -C /go/src/golang.org/x/tools checkout -b current aa82965741a9fecd12b026fbb3d3c6ed3231b8f8 && \
     go install golang.org/x/tools/cmd/goimports
 RUN rm -rf /go/src /go/pkg