Bump to go 1.19

[coveralls]

Pull Request Test Coverage Report for Build 3532370970

• 5 of 28 (17.86%) changed or added relevant lines in 19 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 15.179%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/policy/build.go	0	1	0.0%
cmd/policy/inspect.go	0	1	0.0%
cmd/policy/login.go	0	1	0.0%
cmd/policy/pull.go	0	1	0.0%
cmd/policy/push.go	0	1	0.0%
cmd/policy/repl.go	0	1	0.0%
cmd/policy/rm.go	0	1	0.0%
cmd/policy/save.go	0	1	0.0%
cmd/policy/tag.go	0	1	0.0%
cmd/policy/version.go	0	1	0.0%
<!--	Total:	5	28	17.86%	-->

Files with Coverage Reduction	New Missed Lines	%
pkg/app/init.go	1	0%
<!--	Total:	1		-->

Totals
Change from base Build 3336231845:	0.0%
Covered Lines:	512
Relevant Lines:	3373

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💛 - Coveralls

[gertd]

@oanatmaria the .envrc file contains export GOFLAGS=-mod=mod which when set result in the inability to build

go: -mod may only be set to readonly when in workspace mode, but it is set to "mod"
    Remove the -mod flag to use the default readonly value,
    or set GOWORK=off to disable workspace mode.
Error: error compiling magefiles

Not clear why it was originally added, but I guess this should be removed