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Static IP guide

Making API requests with a static IP from a Go app on Fly.io

Fly.io and Go pair naturally, and so do Go and proxies: http.ProxyURL(fixieURL) on a Transport is the whole integration. With FIXIE_URL stored as a Fly secret, every machine in every region makes API calls from the same two static addresses.

RuntimeGo
PlatformFly.io
DestinationAPI allowlisting
Fixie productFixie HTTP/S proxy

Recommended setup

Use Fixie HTTP/S proxy for HTTP and HTTPS requests to an API, webhook provider, or service that allowlists outbound IP addresses. Store the proxy value in FIXIE_URL, then configure Go to route outbound traffic through Fixie before connecting to API allowlisting.

Set up Fixie on Fly.io

Create a Fixie HTTP/S proxy in the Fixie dashboard. Copy the proxy value into Fly.io secrets as FIXIE_URL, and copy the outbound IPs into the destination allowlist.

Set a Fly.io secret

fly secrets set FIXIE_URL=...

Implementation

The example below shows the core application-side change. Keep credentials in environment variables and avoid committing proxy, database, or API secrets.

Make an HTTP request through FIXIE_URL

package main

import (
  "net/http"
  "net/url"
  "os"
)

func main() {
  fixieURL, err := url.Parse(os.Getenv("FIXIE_URL"))
  if err != nil {
    panic(err)
  }

  client := &http.Client{
    Transport: &http.Transport{Proxy: http.ProxyURL(fixieURL)},
  }

  _, err = client.Get("https://api.example.com/data")
  if err != nil {
    panic(err)
  }
}

Good to know

  • The default transport honors HTTPS_PROXY, so setting that secret to the Fixie URL also proxies third-party SDKs that construct clients from defaults.
  • Fly regions span the globe — pick the Fixie region closest to where your machines actually run, not where you deploy from.

Allowlist and test the static IPs

  1. Open the Fixie dashboard and copy the outbound IP addresses for this proxy.
  2. Add both IPs to the API provider.
  3. Deploy the updated Go app on Fly.io.
  4. Run a small connection test before sending production traffic.

Related guides

Related docs