go: upgrade to Go 1.26 and modernize#34

ggilmore wants to merge 8 commits into

mainsourcegraph/go-jsonschema:mainfrom

go-fix-modernize--270b1737-ed47-45a7-86f7-80feb79e95f9sourcegraph/go-jsonschema:go-fix-modernize--270b1737-ed47-45a7-86f7-80feb79e95f9Copy head branch name to clipboard