fix module again

Dockerfile

@@ -2,7 +2,7 @@ FROM golang:1.11-alpine as builder
 RUN apk --no-cache add git gcc musl-dev
 WORKDIR /go/src/git.lattuga.net/boyska/feedpanel/
 COPY ./ /go/src/git.lattuga.net/boyska/feedpanel/
-ENV GO111MODULES=on
+ENV GO111MODULE=on
 RUN go get ./... && CGO_ENABLED=0 GOOS=linux go install ./...
 
 FROM busybox