Go

Build with Flox

Not only can you develop your software with Flox, but you can build it as well. See the builds concept page for more details.

Manifest builds

Since the output of the build must be copied to the $out directory, you may either install the output directly to $out, or you may copy the executable there manually after running go build.

Install directly to $out:

[build.myproject]
command = '''
  GOBIN=$out/bin go install -trimpath
'''

Copy the executable manually:

[build.myproject]
command = '''
  mkdir -p $out/bin
  go build -trimpath
  cp ./myproject $out/bin/myproject
'''

Go compiler adds metadata

Go adds metadata to compiled binaries that allows details from the build environment to leak through. For example, a compiled binary will contain absolute paths to source files. This can cause builds to fail as it interferes with Flox's ability to determine when a build depends on an artifact that aren't included in the build's closure, i.e. when a build has missing dependencies. To address this you'll need to compile your programs with the -trimpath option.

Go builds depend on iana, mailcap, tzdata

The Go net/http package has a few runtime dependencies that you may not know you depend on:

• iana-etc: used to resolve a protocol or service by name.
• mailcap: used to resolve MIME types.
• tzdata: used to resolve timezones.

You'll need to add those packages to your environment

[install]
iana-etc.pkg-path = "iana-etc"
mailcap.pkg-path = "mailcap"
tzdata.pkg-path = "tzdata"

and add them to the runtime-packages of your build if you're limiting which packages are present at runtime:

runtime-packages = [
  "iana-etc",
  "mailcap",
  "tzdata",
]

Vendoring dependencies in pure builds

As discussed in the pure builds of the Builds concept page, pure builds run in a sandbox without network access on Linux. A pure build can be run as a multi-stage build where the first step vendors dependencies. An example is shown below:

[build.myproject-deps]
command = '''
  export GOMODCACHE=$out
  go mod download -modcacherw
'''

[build.myproject]
command = """
  export GOMODCACHE=${myproject-deps}
  mkdir -p "$out/bin"
  go build -trimpath -o $out/bin/myproject
  chmod +x $out/bin/myproject
"""
sandbox = "pure"

Nix expression builds

To build a project using buildGoModule which will import your existing dependency file, but you will need to update the hash:

{ buildGoModule }:

buildGoModule {
  pname = "myproject";
  version = "0.1.0";
  src = ../../../.;

  vendorHash = "<YOUR_HASH>";
}