Transmit/Receive data Nodemcu(V3) + Bluetooth Module HC-05
I had the exact same problem and got it to work doing these changes:
I had to add this under my library include statements
#ifndef D5
#if defined(ESP8266)
#define D5 (14)
#define D6 (12)
#define D7 (13)
#define D8 (15)
#define TX (1)
#endif
#endif

and changed
SoftwareSerial BTserial(3, 1); // RX, TX
to
SoftwareSerial BTserial(D5,D6);
I used D5 and D6 on my esp8266 instead of D1 and D3 but shouldn't matter