can't build on ARM (32bit armv7l)(armhf)

[victort]

getting the following trying to build:

$ docker build -t test/sshfs .
Sending build context to Docker daemon  6.286MB
Step 1/10 : FROM golang:1.9-alpine as builder
1.9-alpine: Pulling from library/golang
0864efeeb5cb: Pull complete
3cda69762aee: Pull complete
560245ac5034: Pull complete
586edbca9a8a: Pull complete
6eaf7d950ae3: Pull complete
c758fece5e11: Pull complete
40d8cc73c33b: Pull complete
Digest: sha256:102459ffe9132ccafe6601a1a7dd1b54f6fb3d2550113eb65dfa018aa76e2126
Status: Downloaded newer image for golang:1.9-alpine
 ---> 978b3dde7adc
Step 2/10 : COPY . /go/src/github.com/vieux/docker-volume-sshfs
 ---> 11d683e4266e
Step 3/10 : WORKDIR /go/src/github.com/vieux/docker-volume-sshfs
Removing intermediate container bb29b9847417
 ---> dd8edf15e71c
Step 4/10 : RUN set -ex     && apk add --no-cache --virtual .build-deps     gcc libc-dev     && go install --ldflags '-extldflags "-static"'     && apk del .build-deps
 ---> Running in 967527a2f059
+ apk add --no-cache --virtual .build-deps gcc libc-dev
fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/main/armhf/APKINDEX.tar.gz
WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.6/main/armhf/APKINDEX.tar.gz: temporary error (try again later)
fetch http://dl-cdn.alpinelinux.org/alpine/v3.6/community/armhf/APKINDEX.tar.gz
WARNING: Ignoring http://dl-cdn.alpinelinux.org/alpine/v3.6/community/armhf/APKINDEX.tar.gz: temporary error (try again later)
ERROR: unsatisfiable constraints:
  .build-deps-0:
    masked in: cache
    satisfies: world[.build-deps]
  gcc (missing):
    required by:
  libc-dev (missing):
    required by:
The command '/bin/sh -c set -ex     && apk add --no-cache --virtual .build-deps     gcc libc-dev     && go install --ldflags '-extldflags "-static"'     && apk del .build-deps' returned a non-zero code: 3

docker:

$ docker version
Client:
 Version:       18.02.0-ce
 API version:   1.36
 Go version:    go1.9.3
 Git commit:    fc4de44
 Built: Wed Feb  7 21:24:08 2018
 OS/Arch:       linux/arm
 Experimental:  false
 Orchestrator:  swarm

Server:
 Engine:
  Version:      18.02.0-ce
  API version:  1.36 (minimum version 1.12)
  Go version:   go1.9.3
  Git commit:   fc4de44
  Built:        Wed Feb  7 21:20:13 2018
  OS/Arch:      linux/arm
  Experimental: false