Building Go app with "vendor" directory on Jenkins with Docker

I'm trying to set up a Jenkins Pipeline to build and deploy my first Go project using a <code>Jenkinsfile</code> and <code>docker.image().inside </code>. I can't figure out how to get go to pick up the dependencies in the <code>vendor/</code> directory.

When I run the build, I get a bunch of errors:
<pre>

• goapp test ./...
  src/dao/demo_dao.go:8:2: cannot find package "github.com/dgrijalva/jwt-go" in any of:
  /usr/lib/go_appengine/goroot/src/github.com/dgrijalva/jwt-go (from $GOROOT)
  /usr/lib/go_appengine/gopath/src/github.com/dgrijalva/jwt-go (from $GOPATH)
  /workspace/src/github.com/dgrijalva/jwt-go
  </pre>

...why isn't it picking up the Vendor directory?

When I throw in some logging, it seems that after running <code>sh "cd /workspace/src/bitbucket.org/nalbion/go-demo"</code> the next <code>sh</code> command is still in the original <code>${WORKSPACE}</code> directory. I really like the idea of the Jenkins file, but I can't find any decent documentation for it.

(Edit - there is decent documentation here but <code>dir("/workspace/src/bitbucket.org/nalbion/go-demo") {}</code> doesn't seem to work within <code>docker.image().inside)</code>

My Docker file resembles:
<pre>
FROM golang:1.6.2

Google's App Engine Go SDK

RUN wget https://storage.googleapis.com/appengine-sdks/featured/go_appengine_sdk_linux_amd64-1.9.40.zip -q -O go_appengine_sdk.zip &&
unzip -q go_appengine_sdk.zip -d /usr/lib/ &&
rm go_appengine_sdk.zip
ENV PATH /usr/lib/go_appengine:/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
ENV GOPATH /usr/lib/go_appengine/gopath

Add Jenkins user

RUN groupadd -g 132 jenkins && useradd -d "/var/jenkins_home" -u 122 -g 132 -m -s /bin/bash jenkins
</pre>

And my Jenkinsfile:
<pre>
node('docker') {
currentBuild.result = "SUCCESS"

try {
    stage 'Checkout'
    checkout scm

    stage 'Build and Test'
    env.WORKSPACE = pwd()
    docker.image('nalbion/go-web-build:latest').inside(
            "-v ${env.WORKSPACE}:/workspace/src/bitbucket.org/nalbion/go-demo " +
            "-e GOPATH=/usr/lib/go_appengine/gopath:/workspace") {

        // Debugging
        sh 'echo GOPATH: $GOPATH'
        sh "ls -al /workspace/src/bitbucket.org/nalbion/go-demo"
        sh "cd /workspace/src/bitbucket.org/nalbion/go-demo"
        sh "pwd"

        sh "go vet ./src/..."
        sh "goapp test ./..."
    }

    stage 'Deploy to DEV'
    docker.image('nalbion/go-web-build').inside {
        sh "goapp deploy --application go-demo --version v${v} app.yaml"
    }

    timeout(time:5, unit:'DAYS') {
        input message:'Approve deployment?', submitter: 'qa'
    }

    stage 'Deploy to PROD'
    docker.image('nalbion/go-web-build').inside {
        sh "goapp deploy --application go-demo --version v${v} app.yaml"
    }
} catch (err) {
    currentBuild.result = "FAILURE"
    // send notifications
    throw err
}

}
</pre>

I managed to get it working by including the <code>cd</code> in the same <code>sh</code> statement:

<pre>
docker.image('nalbion/go-web-build:latest')
.inside("-v ${env.WORKSPACE}:/workspace/src/bitbucket.org/nalbion/go-demo " +
"-e GOPATH=/usr/lib/go_appengine/gopath:/workspace") {
sh """
cd /workspace/src/bitbucket.org/nalbion/go-demo
go vet ./src/...
goapp test ./...
"""
}
</pre>