Change tree type in router struct

[bmf-san]

Description

see: #84

Changes

changes tree type in router struct.

benchmark tests

goos: darwin
goarch: arm64
pkg: github.com/bmf-san/goblin
BenchmarkSetRoutes1  	1000000000	         0.0000022 ns/op	       0 B/op	       0 allocs/op
BenchmarkSetRoutes5  	1000000000	         0.0000018 ns/op	       0 B/op	       0 allocs/op
BenchmarkSetRoutes10 	1000000000	         0.0000025 ns/op	       0 B/op	       0 allocs/op
BenchmarkStatic1     	18641005	        57.88 ns/op	       0 B/op	       0 allocs/op
BenchmarkStatic5     	 6875048	       176.5 ns/op	       0 B/op	       0 allocs/op
BenchmarkStatic10    	 3714705	       359.5 ns/op	       0 B/op	       0 allocs/op
BenchmarkWildCard1   	 5812250	       204.0 ns/op	     328 B/op	       3 allocs/op
BenchmarkWildCard5   	 2605432	       467.2 ns/op	     408 B/op	       3 allocs/op
BenchmarkWildCard10  	 1501742	       853.4 ns/op	     609 B/op	       3 allocs/op
BenchmarkRegexp1     	 3698962	       338.7 ns/op	     336 B/op	       4 allocs/op
BenchmarkRegexp5     	 1000000	      1122 ns/op	     460 B/op	       8 allocs/op
BenchmarkRegexp10    	  647394	      1910 ns/op	     694 B/op	      13 allocs/op
PASS
ok  	github.com/bmf-san/goblin	13.507s

Impact range

No specification changes

Operational Requirements

N/A

Related Issue

#84

Supplement

N/A