Document how to use dep with Docker

docs/FAQ.md

@@ -26,6 +26,7 @@ Summarize the question and quote the reply, linking back to the original comment
 * [How does `dep` handle symbolic links?](#how-does-dep-handle-symbolic-links)
 * [Does `dep` support relative imports?](#does-dep-support-relative-imports)
 * [How do I make `dep` resolve dependencies from my `GOPATH`?](#how-do-i-make-dep-resolve-dependencies-from-my-gopath)
+* [How do I use `dep` with Docker?](#how-do-i-use-dep-with-docker)
 
 ## Best Practices
 * [Should I commit my vendor directory?](#should-i-commit-my-vendor-directory)
@@ -288,6 +289,39 @@ For a refresher on Go's recommended workspace organization, see the ["How To Wri
 `dep init -gopath`, which falls back to network mode when the packages are not
 found in `GOPATH`. `dep ensure` doesn't work with projects in `GOPATH`.
 
+## How do I use `dep` with Docker?
+
+`dep ensure -vendor-only` creates the vendor folder from a valid `Gopkg.toml` and `Gopkg.lock` without checking for Go code.
+This is especially useful for builds inside docker utilizing cache layers.
+
+Sample dockerfile:
+
+    FROM golang:1.8 AS builder
+
+    RUN curl -fsSL -o /usr/local/bin/dep https://github.com/golang/dep/releases/download/vX.X.X/dep-linux-amd64 && chmod +x /usr/local/bin/dep
+
+    RUN mkdir -p /go/src/github.com/***
+    WORKDIR /go/src/github.com/***
+
+    COPY Gopkg.toml Gopkg.lock ./
+    # copies the Gopkg.toml and Gopkg.lock to WORKDIR
+
+    RUN dep ensure -vendor-only
+    # install the dependencies without checking for go code
+    COPY . .
+    # copies any other required code to the WORKDIR
+    RUN go build -o *** 
+    # the -o flag is used to specify the name of the executable to be installed
+
+    FROM alpine:latest
+    RUN apk --no-cache add ca-certificates
+
+    WORKDIR /root/
+
+    COPY --from=builder /go/src/github.com/***  .
+    # copies only the built executable to the new image
+    ENTRYPOINT ["./***"]
+
 
 ## Best Practices
 ### Should I commit my vendor directory?