Dockerfile: Make it build with Go 1.18

diff --git a/Dockerfile b/Dockerfile
index fcae03f5484557733d02a7bd14f1c804e7bc2bbf..885809fabf238b3a914f08a92d70da75a091a43d 100755 (executable)
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,7 +2,7 @@
 # Twitter:      https://twitter.com/gohugoio
 # Website:      https://gohugo.io/
 
-FROM golang:1.16-alpine AS build
+FROM golang:1.18-alpine AS build
 
 # Optionally set HUGO_BUILD_TAGS to "extended" or "nodeploy" when building like so:
 #   docker build --build-arg HUGO_BUILD_TAGS=extended .
@@ -20,7 +20,7 @@ COPY . /go/src/github.com/gohugoio/hugo/
 # gcc/g++ are required to build SASS libraries for extended version
 RUN apk update && \
     apk add --no-cache gcc g++ musl-dev git && \
-    go get github.com/magefile/mage
+    go install github.com/magefile/mage
 
 RUN mage hugo && mage install