chore: use t.Setenv to set env vars in tests

[Juneezee]

Starting from Go 1.17, we can use t.Setenv to set environment variable in test. The environment variable is automatically restored to its original value when the test and all its subtests complete. This ensures that each test does not start with leftover environment variables from previous completed tests.

Reference: https://pkg.go.dev/testing#T.Setenv

func TestFoo(t *testing.T) {
	// before
	os.Setenv(key, "new value")
	defer os.Unsetenv(key)
	
	// after
	t.Setenv(key, "new value")
}

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[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (ef8dae8) 49.74% compared to head (b7456b5) 49.75%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #14377   +/-   ##
=======================================
  Coverage   49.74%   49.75%           
=======================================
  Files         261      261           
  Lines       44676    44676           
=======================================
+ Hits        22225    22229    +4     
+ Misses      20262    20259    -3     
+ Partials     2189     2188    -1     

see 1 file with indirect coverage changes

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[blakepettersson]

One minor nit, otherwise LGTM! 🍾

[crenshaw-dev]

Lovely. Thank you, @Juneezee!