Build fails: caddy v2.10.2 requires Go >= 1.25 but frankenphp:builder ships Go 1.24.x

[Spomky]

What happened?

When building a custom FrankenPHP binary with extra Caddy modules using the official dunglas/frankenphp:builder image, the build fails because the image ships Go 1.24.x, while caddy/v2.10.2 now requires Go ≥ 1.25.
Occurs only on amd64, not on arm64.

Setting ENV GOTOOLCHAIN=go1.25+auto (or ENV GOTOOLCHAIN=auto) just before the build is a quick fix

The Dockerfile is available here: https://github.com/Spomky-Labs/phpwa-demo/blob/main/Dockerfile

Build Type

Custom (tell us more in the description)

Worker Mode

No

Operating System

GNU/Linux

CPU Architecture

x86_64

PHP configuration

Not relevant here.

Relevant log output

> 0.070 2025/08/24 13:29:24 [INFO] exec (timeout=0s): /usr/local/go/bin/go get -v -ldflags=-w -s -tags=nobadger,nomysql,nopgx github.com/caddyserver/caddy/v2 
0.422 go: downloading github.com/caddyserver/caddy/v2 v2.10.2
0.442 go: downloading github.com/caddyserver/caddy v1.0.5
0.706 go: github.com/caddyserver/caddy/v2@v2.10.2 requires go >= 1.25 (running go 1.24.5; GOTOOLCHAIN=local)
0.708 2025/08/24 13:29:24 [FATAL] exit status 1

[henderkes]

Will be fixed with the next release: #1811

[dunglas]

I'm on it

[Spomky]

Thanks for pointing that out. I had missed it