fatal error: sync: unlock of unlocked mutex

[xoba]

error happens on the line marked "ERROR" below (mvdb.go:36), re v0.0.0-20181213202341-817cee58a244 (btw, it would be great for this repo to be tagged with its own semantic version releases instead):

		db, err := sql.Open("ramsql", "")
		if err != nil {
			return err
		}
		defer db.Close()
		if err := db.Ping(); err != nil {
			return err
		}
		if _, err := db.Exec("CREATE TABLE address (id int, street text)"); err != nil {
			return err
		}
		stmt, err := db.Prepare("insert into address (id,street) values (?,?)")
		if err != nil {
			return err
		}
		for i := 0; i < 10; i++ {
			if _, err := stmt.Exec(i, fmt.Sprintf("%d park ave", 100+i)); err != nil { // ERROR
				return err
			}
		}

and the stack trace is as follows:

goroutine 1 [running]:
runtime.throw(0x17ffa41, 0x1e)
	/Users/mra/go/src/runtime/panic.go:774 +0x72 fp=0xc0007118e0 sp=0xc0007118b0 pc=0x102f742
sync.throw(0x17ffa41, 0x1e)
	/Users/mra/go/src/runtime/panic.go:760 +0x35 fp=0xc000711900 sp=0xc0007118e0 pc=0x102f6c5
sync.(*Mutex).unlockSlow(0xc000208000, 0xc0ffffffff)
	/Users/mra/go/src/sync/mutex.go:196 +0xd6 fp=0xc000711928 sp=0xc000711900 pc=0x1069b36
sync.(*Mutex).Unlock(0xc000208000)
	/Users/mra/go/src/sync/mutex.go:190 +0x48 fp=0xc000711948 sp=0xc000711928 pc=0x1069a48
github.com/proullon/ramsql/driver.(*Stmt).Exec(0xc000208260, 0xc000208500, 0x2, 0x2, 0x1a0f480, 0xc000208720, 0x0, 0x0)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/driver/stmt.go:108 +0x400 fp=0xc000711a48 sp=0xc000711948 pc=0x1676950
database/sql.ctxDriverStmtExec(0x1a17f00, 0xc0000d6030, 0x1a18180, 0xc000208260, 0xc000238e60, 0x2, 0x2, 0x2, 0x2, 0x0, ...)
	/Users/mra/go/src/database/sql/ctxutil.go:77 +0x165 fp=0xc000711ac0 sp=0xc000711a48 pc=0x1437985
database/sql.resultFromStatement(0x1a17f00, 0xc0000d6030, 0x1a15680, 0xc000208000, 0xc0000f8400, 0xc000711da8, 0x2, 0x2, 0x0, 0x0, ...)
	/Users/mra/go/src/database/sql/sql.go:2435 +0x156 fp=0xc000711b80 sp=0xc000711ac0 pc=0x1442e56
database/sql.(*Stmt).ExecContext(0xc0001e0900, 0x1a17f00, 0xc0000d6030, 0xc000711da8, 0x2, 0x2, 0x0, 0x0, 0x0, 0x0)
	/Users/mra/go/src/database/sql/sql.go:2411 +0x1f9 fp=0xc000711c60 sp=0xc000711b80 pc=0x1442ae9
database/sql.(*Stmt).Exec(...)
	/Users/mra/go/src/database/sql/sql.go:2423
github.com/xoba/ds/a/mv.glob..func10(0xc0000d4360, 0x0, 0x0, 0x0, 0x0, 0x0)
	/Users/mra/ds/a/mv/mvdb.go:36 +0x374 fp=0xc000711e18 sp=0xc000711c60 pc=0x16789e4
github.com/xoba/ds/a/cmd.RunCommand(0x17e9dc0, 0x3, 0x180e01c, 0x33, 0x185dc78, 0x0, 0x0, 0x0, 0xc000711ef0, 0x103d28a)
	/Users/mra/ds/a/cmd/cmd.go:66 +0xe9 fp=0xc000711e80 sp=0xc000711e18 pc=0x111daa9
github.com/xoba/ds/a/zexe.RunAsMain(0x17e9dc0, 0x3, 0x180e01c, 0x33, 0x185dc78)
	/Users/mra/ds/a/zexe/zexe.go:18 +0x84 fp=0xc000711f00 sp=0xc000711e80 pc=0x1678e74
main.main()
	/Users/mra/ds/a/zexe/mdb/mdb_exe.go:13 +0x8f fp=0xc000711f60 sp=0xc000711f00 pc=0x1678fef
runtime.main()
	/Users/mra/go/src/runtime/proc.go:203 +0x21e fp=0xc000711fe0 sp=0xc000711f60 pc=0x10310ce
runtime.goexit()
	/Users/mra/go/src/runtime/asm_amd64.s:1357 +0x1 fp=0xc000711fe8 sp=0xc000711fe0 pc=0x105bce1

goroutine 50 [select]:
database/sql.(*DB).connectionOpener(0xc000228000, 0x1a17ec0, 0xc00025b900)
	/Users/mra/go/src/database/sql/sql.go:1052 +0xe8
created by database/sql.OpenDB
	/Users/mra/go/src/database/sql/sql.go:722 +0x15d

goroutine 51 [select]:
database/sql.(*DB).connectionResetter(0xc000228000, 0x1a17ec0, 0xc00025b900)
	/Users/mra/go/src/database/sql/sql.go:1065 +0xfb
created by database/sql.OpenDB
	/Users/mra/go/src/database/sql/sql.go:723 +0x193

goroutine 52 [select]:
github.com/proullon/ramsql/engine.(*Engine).listen(0xc0002067e0)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:111 +0x13b
created by github.com/proullon/ramsql/engine.(*Engine).start
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:64 +0x3f

goroutine 53 [chan receive]:
github.com/proullon/ramsql/engine/protocol.(*ChannelEngineEndpoint).Accept(0xc000010018, 0xc000485fb0, 0xc000010028, 0x0, 0x0)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/protocol/channel.go:81 +0x45
github.com/proullon/ramsql/engine.(*Engine).listen.func1(0xc0002067e0, 0xc0000aeb40)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:100 +0x63
created by github.com/proullon/ramsql/engine.(*Engine).listen
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:98 +0x7c

goroutine 54 [chan receive]:
github.com/proullon/ramsql/engine/protocol.(*ChannelEngineConn).ReadStatement(0xc000010028, 0xc0002086c0, 0x1, 0x1, 0x1a1b000)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/protocol/channel.go:109 +0x52
github.com/proullon/ramsql/engine.(*Engine).handleConnection(0xc0002067e0, 0x1a1b000, 0xc000010028)
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:127 +0x3b
created by github.com/proullon/ramsql/engine.(*Engine).listen
	/Users/mra/gopath/pkg/mod/github.com/proullon/[email protected]/engine/engine.go:113 +0xb7