$ mongoreplay play -vvv -ddd --playback-file xxx.bson --no-preprocess --no-truncate
...
2020/10/15 14:35:41 Socket 0xc0001f61c0 to localhost:27017: sending 1 op(s) (190714 bytes)
2020/10/15 14:35:41 (Connection 9) op RawOp: query
2020/10/15 14:35:41 (Connection 10) op RawOp: message
2020/10/15 14:35:41 (Connection 11) op RawOp: message
2020/10/15 14:35:41 Socket 0xc0001f60e0 to localhost:27017: serializing op: &mgo.QueryOp{Collection:"admin.$cmd", Query:(*bson.Raw)(0xc001e8d4a0), Skip:0, Limit:-1, Selector:interface {}(nil), Flags:0x0, replyFunc:(mgo.replyFunc)(0x435a9b0), mode:0, Options:mgo.QueryWrapper{Query:interface {}(nil), OrderBy:interface {}(nil), Hint:interface {}(nil), Explain:false, Snapshot:false, ReadPreference:bson.D(nil), MaxScan:0, MaxTimeMS:0, Comment:""}, HasOptions:false, ServerTags:[]bson.D(nil)}
2020/10/15 14:35:41 Socket 0xc0001f62a0 to localhost:27017: closing: Closed explicitly (abend=false)
2020/10/15 14:35:41 (Connection 14) op RawOp: message
panic: runtime error: index out of range

goroutine 139 [running]:
github.com/mongodb/mongo-tools/mongoreplay.(*MsgOp).getCommandName(0xc0002d0120, 0x0, 0x0, 0x0, 0x1)
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/msg_op.go:393 +0x31b
github.com/mongodb/mongo-tools/mongoreplay.(*MsgOp).FromReader(0xc0002d0120, 0x4702580, 0xc00231a210, 0x2840, 0xc0002d0720)
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/msg_op.go:128 +0x268
github.com/mongodb/mongo-tools/mongoreplay.(*RawOp).Parse(0xc0004883f0, 0x10e000, 0x36, 0x0, 0x0)
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/raw_op.go:177 +0x186
github.com/mongodb/mongo-tools/mongoreplay.(*ExecutionContext).Execute(0xc000358050, 0xc0004883f0, 0xc0001f62a0, 0xc0002e7f60, 0x2, 0x2, 0xe, 0x400767c, 0xc00037c780)
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/execute.go:229 +0x42
github.com/mongodb/mongo-tools/mongoreplay.(*ExecutionContext).newExecutionConnection.func1(0xbfda437f0fab710e, 0x1439849d, 0x4ae8f40, 0xc000358050, 0xd, 0xc000084240)
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/execute.go:204 +0x3ad
created by github.com/mongodb/mongo-tools/mongoreplay.(*ExecutionContext).newExecutionConnection
	/data/mci/fe05bde3691836bca0e4a60c44ec1a8a/src/src/mongo/gotools/src/github.com/mongodb/mongo-tools/mongoreplay/execute.go:175 +0xb5