$ cat snapcraft.yaml 
name: prometheus
version: 1.6.1
grade: stable
summary: The Prometheus monitoring system and time series database
description: |
  Prometheus is a systems and service monitoring system. It collects metrics from configured targets at given intervals, evaluates rule expressions, displays the results, and can trigger alerts if some condition is observed to be true.
confinement: strict
apps:
  prometheus:
    command: 'bin/prometheus.wrapper'
    plugs: [network-bind, network, content]
    daemon: simple
  promtool:
    command: 'bin/promtool'
  storagetool:
    command: 'bin/storagetool'
plugs:
  content:
    content: promreg
    target: $SNAP_DATA/promreg
parts:
  prometheus:
    plugin: go
    source: https://github.com/prometheus/prometheus.git
    source-tag: v1.6.1
    go-importpath: github.com/prometheus/prometheus
  example-config:
    plugin: dump
    source: https://github.com/prometheus/prometheus.git
    source-tag: v1.6.1
    source-type: git
    organize:
      documentation/examples/prometheus.yml: etc/prometheus/prometheus.yml.example
    stage:
      - etc/prometheus/prometheus.yml.example
    prime:
      - etc/prometheus/prometheus.yml.example
  snap-wrappers:
    plugin: dump
    source: .
    organize:
      snap_config_wrapper: bin/prometheus.wrapper
      daemon_arguments: etc/prometheus/daemon_arguments.example
    stage:
      - bin/prometheus.wrapper
      - etc/prometheus/daemon_arguments.example
    prime:
      - bin/prometheus.wrapper
      - etc/prometheus/daemon_arguments.example
$ snapcraft 
Preparing to pull prometheus 
Pulling prometheus 
Cloning into '/home/jacek/build/prometheus-snap/parts/prometheus/src'...
remote: Counting objects: 26217, done.
remote: Compressing objects: 100% (75/75), done.
remote: Total 26217 (delta 14), reused 0 (delta 0), pack-reused 26137
Receiving objects: 100% (26217/26217), 20.84 MiB | 2.36 MiB/s, done.
Resolving deltas: 100% (14274/14274), done.
Checking connectivity... done.
Note: checking out '4666df502c0e239ed4aa1d80abbbfb54f61b23c3'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b <new-branch-name>

go get -t -d ./github.com/prometheus/prometheus/...
package context: unrecognized import path "context" (import path does not begin with hostname)
Command '['/bin/sh', '/tmp/tmpx7s1mf6j', 'go', 'get', '-t', '-d', './github.com/prometheus/prometheus/...']' returned non-zero exit status 1