Try updating the machine image instead of installing docker via script

Author: Richard Connon

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     machine:
-      image: circleci/classic:201708-01
+      image: circleci/classic:latest
     working_directory: ~/go/src/github.com/fnproject/fn
     environment: # apparently expansion doesn't work here yet: https://discuss.circleci.com/t/environment-variable-expansion-in-working-directory/11322
       - GOPATH=/home/circleci/go
@@ -22,12 +22,6 @@ jobs:
           wget https://storage.googleapis.com/golang/go$GOVERSION.$OS-$ARCH.tar.gz
           sudo tar -C /usr/local -xzf go$GOVERSION.$OS-$ARCH.tar.gz
       - run: go version
-      # install latest Docker
-      - run: |
-          sudo rm -rf /var/cache/apt/archives && sudo ln -s ~/.apt-cache /var/cache/apt/archives && mkdir -p ~/.apt-cache/partial
-          sudo service docker stop
-          curl -fsSL https://get.docker.com/ | sudo sh
-          docker version
       - run: docker version
       - run: nproc
       # fixes git-diff warning: "warning: inexact rename detection was skipped due to too many files.""