update go version 1.19.x -> 1.20.x on GitHub Action

[rmatsuoka]

GitHub Actions are failed with a following error message.
According to golang/go#51007 (comment), this error may be fixed by updating go version on GHA.

C:\hostedtoolcache\windows\go\1.19.13\x64\pkg\tool\windows_amd64\link.exe: running gcc failed: exit status 1
C:/ProgramData/Chocolatey/lib/mingw/tools/install/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\RUNNER~1\AppData\Local\Temp\go-link-81374[21](https://github.com/mackerelio/mackerel-agent/actions/runs/6269488095/job/17025983130?pr=932#step:6:22)57\000005.o: in function `_cgo_preinit_init':
\\_\_\runtime\cgo/gcc_libinit_windows.c:40: undefined reference to `__imp___iob_func'
C:/ProgramData/Chocolatey/lib/mingw/tools/install/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\RUNNER~1\AppData\Local\Temp\go-link-813742157\000005.o: in function `x_cgo_notify_runtime_init_done':
\\_\_\runtime\cgo/gcc_libinit_windows.c:105: undefined reference to `__imp___iob_func'
C:/ProgramData/Chocolatey/lib/mingw/tools/install/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\RUNNER~1\AppData\Local\Temp\go-link-813742157\000005.o: in function `_cgo_beginthread':
\\_\_\runtime\cgo/gcc_libinit_windows.c:149: undefined reference to `__imp___iob_func'
C:/ProgramData/Chocolatey/lib/mingw/tools/install/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\Users\RUNNER~1\AppData\Local\Temp\go-link-813742157\000006.o: in function `x_cgo_thread_start':
\\_\_\runtime\cgo/gcc_util.c:18: undefined reference to `__imp___iob_func'
collect2.exe: error: ld returned 1 exit status