First benchmark!

~/s/g/p/g/benchmark$ go test -bench=.
goos: linux
goarch: amd64
pkg: github.com/pelletier/go-toml/v2/benchmark
cpu: Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
BenchmarkUnmarshalSimple/v2-8         	 1607115	       742.0 ns/op
BenchmarkUnmarshalSimple/v1-8         	  307977	      3915 ns/op
BenchmarkUnmarshalSimple/bs-8         	  516754	      2330 ns/op
BenchmarkReferenceFile/v2-8           	    9604	    129158 ns/op	  111422 B/op	    1381 allocs/op
BenchmarkReferenceFile/v1-8           	    4521	    263808 ns/op	  130566 B/op	    2649 allocs/op
BenchmarkReferenceFile/bs-8           	    4070	    296271 ns/op	   80784 B/op	    1729 allocs/op
PASS
ok  	github.com/pelletier/go-toml/v2/benchmark	8.139s

benchmark/benchmark_test.go

@@ -0,0 +1,178 @@
+package benchmark_test
+
+import (
+	"io/ioutil"
+	"testing"
+	"time"
+
+	tomlbs "github.com/BurntSushi/toml"
+	tomlv1 "github.com/pelletier/go-toml-v1"
+	"github.com/pelletier/go-toml/v2"
+	"github.com/stretchr/testify/require"
+)
+
+type runner struct {
+	name      string
+	unmarshal func([]byte, interface{}) error
+}
+
+var runners = []runner{
+	{"v2", toml.Unmarshal},
+	{"v1", tomlv1.Unmarshal},
+	{"bs", tomlbs.Unmarshal},
+}
+
+func bench(b *testing.B, f func(r runner, b *testing.B)) {
+	for _, r := range runners {
+		b.Run(r.name, func(b *testing.B) {
+			f(r, b)
+		})
+	}
+}
+
+func BenchmarkUnmarshalSimple(b *testing.B) {
+	bench(b, func(r runner, b *testing.B) {
+		d := struct {
+			A string
+		}{}
+		doc := []byte(`A = "hello"`)
+		for i := 0; i < b.N; i++ {
+			err := r.unmarshal(doc, &d)
+			if err != nil {
+				panic(err)
+			}
+		}
+	})
+}
+
+type benchmarkDoc struct {
+	Table struct {
+		Key      string
+		Subtable struct {
+			Key string
+		}
+		Inline struct {
+			Name struct {
+				First string
+				Last  string
+			}
+			Point struct {
+				X int64
+				U int64
+			}
+		}
+	}
+	String struct {
+		Basic struct {
+			Basic string
+		}
+		Multiline struct {
+			Key1      string
+			Key2      string
+			Key3      string
+			Continued struct {
+				Key1 string
+				Key2 string
+				Key3 string
+			}
+		}
+		Literal struct {
+			Winpath   string
+			Winpath2  string
+			Quoted    string
+			Regex     string
+			Multiline struct {
+				Regex2 string
+				Lines  string
+			}
+		}
+	}
+	Integer struct {
+		Key1        int64
+		Key2        int64
+		Key3        int64
+		Key4        int64
+		Underscores struct {
+			Key1 int64
+			Key2 int64
+			Key3 int64
+		}
+	}
+	Float struct {
+		Fractional struct {
+			Key1 float64
+			Key2 float64
+			Key3 float64
+		}
+		Exponent struct {
+			Key1 float64
+			Key2 float64
+			Key3 float64
+		}
+		Both struct {
+			Key float64
+		}
+		Underscores struct {
+			Key1 float64
+			Key2 float64
+		}
+	}
+	Boolean struct {
+		True  bool
+		False bool
+	}
+	Datetime struct {
+		Key1 time.Time
+		Key2 time.Time
+		Key3 time.Time
+	}
+	Array struct {
+		Key1 []int64
+		Key2 []string
+		Key3 [][]int64
+		// TODO: Key4 not supported by go-toml's Unmarshal
+		Key5 []int64
+		Key6 []int64
+	}
+	Products []struct {
+		Name  string
+		Sku   int64
+		Color string
+	}
+	Fruit []struct {
+		Name     string
+		Physical struct {
+			Color   string
+			Shape   string
+			Variety []struct {
+				Name string
+			}
+		}
+	}
+}
+
+func BenchmarkReferenceFile(b *testing.B) {
+	bench(b, func(r runner, b *testing.B) {
+		bytes, err := ioutil.ReadFile("benchmark.toml")
+		if err != nil {
+			b.Fatal(err)
+		}
+		b.ReportAllocs()
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			d := benchmarkDoc{}
+			err := r.unmarshal(bytes, &d)
+			if err != nil {
+				panic(err)
+			}
+		}
+	})
+}
+
+func TestReferenceFile(t *testing.T) {
+	bytes, err := ioutil.ReadFile("benchmark.toml")
+	require.NoError(t, err)
+	d := benchmarkDoc{}
+	err = toml.Unmarshal(bytes, &d)
+	require.NoError(t, err)
+}