Update golang version in testing docker images (#3499)

I think this might be required before trying to upgrade the golang
version in please repository, (#3498) to enable CircleCI setup to run
tests properly

Co-authored-by: roselyn <roselyn@thoughtmachine.net>

Author: SpangleLabs

tools/images/alpine/Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.24-alpine
+FROM golang:1.26-alpine
 LABEL org.opencontainers.image.authors="please <at> thoughtmachine <dot> net"
 LABEL org.opencontainers.image.source=https://github.com/thought-machine/please
 

tools/images/freebsd_builder/Dockerfile

@@ -6,7 +6,7 @@ LABEL org.opencontainers.image.source=https://github.com/thought-machine/please
 RUN apt-get update && apt-get install -y curl git gcc xz-utils && apt-get clean
 
 # Go
-RUN curl -fsSL https://dl.google.com/go/go1.24.1.linux-amd64.tar.gz | tar -xzC /usr/local
+RUN curl -fsSL https://dl.google.com/go/go1.26.1.linux-amd64.tar.gz | tar -xzC /usr/local
 RUN ln -s /usr/local/go/bin/go /usr/local/bin/go && ln -s /usr/local/go/bin/gofmt /usr/local/bin/gofmt
 RUN GOOS=freebsd go install std
 

tools/images/ubuntu/Dockerfile

@@ -16,7 +16,7 @@ RUN truncate -s0 /tmp/preseed.cfg; \
     apt-get clean
 
 # Go - we want a specific package version here.
-RUN curl -fsSL https://dl.google.com/go/go1.24.1.linux-amd64.tar.gz | tar -xzC /usr/local
+RUN curl -fsSL https://dl.google.com/go/go1.26.1.linux-amd64.tar.gz | tar -xzC /usr/local
 RUN ln -s /usr/local/go/bin/go /usr/local/bin/go && ln -s /usr/local/go/bin/gofmt /usr/local/bin/gofmt
 
 # Locale

tools/images/ubuntu_alt/Dockerfile

@@ -11,7 +11,7 @@ RUN apt-get update && \
     apt-get clean
 
 # Go
-RUN curl -fsSL https://dl.google.com/go/go1.23.7.linux-amd64.tar.gz | tar -xzC /usr/local
+RUN curl -fsSL https://dl.google.com/go/go1.26.1.linux-amd64.tar.gz | tar -xzC /usr/local
 RUN ln -s /usr/local/go/bin/go /usr/local/bin/go && ln -s /usr/local/go/bin/gofmt /usr/local/bin/gofmt
 
 # Locale