First commit moves attribute construction under if to only construct them when they are used.

Second commit uses WithAttributeSet() instead of WithAttributes(). This avoids copying the slice, which is not necessary for this code. See https://github.com/open-telemetry/opentelemetry-go/blob/metric/v1.28.0/metric/instrument.go#L349-L368.

Also, a bit of allocations can be removed by constructing the vararg slice one time vs when calling Record() each time.

var sink []string

func abc(vals ...string) {
	sink = vals
}

func BenchmarkFuncCall(b *testing.B) {
	b.ReportAllocs()
	b.ResetTimer()
	arg := []string{"a", "b", "c"}
	for i := 0; i < b.N; i   {
		abc(arg...)
	}
}

The above benchmark gives me these results:

// Pass "a", "b", "c"
BenchmarkFuncCall-10    	43171615	        27.14 ns/op	      48 B/op	       1 allocs/op

// Pass arg...
BenchmarkFuncCall-10    	1000000000	         0.9530 ns/op	       0 B/op	       0 allocs/op

See https://go.dev/ref/spec#Passing_arguments_to_..._parameters.