First commit moves attribute construction underifto only construct them when they are used.

Second commit usesWithAttributeSet()instead ofWithAttributes().This avoids copying the slice, which is not necessary for this code. Seehttps://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 callingRecord()each time.

varsink[]string

funcabc(vals...string) {
sink=vals
}

funcBenchmarkFuncCall(b*testing.B) {
b.ReportAllocs()
b.ResetTimer()
arg:=[]string{"a","b","c"}
fori:=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

Seehttps://go.dev/ref/spec#Passing_arguments_to_..._parameters.

RELEASE NOTES: None