Hi.
Can you better explain your issue?
Regards,
Sara

I was not clear.  I was following example 1_2_Hello_World_WS_SPIFFS in the book and when compiling the following error message appeared: 
Building in release mode
Linking .pio\build\esp32doit-devkit-v1\firmware.elf
c:/users/aorus/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld.exe: .pio\build\esp32doit-devkit-v1\libd4b\libESP Async WebServer.a(WebAuthentication.cpp.o):(.literal._ZL6getMD5PhtPc+0x4): undefined reference to `mbedtls_md5_starts’
c:/users/aorus/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld.exe: .pio\build\esp32doit-devkit-v1\libd4b\libESP Async WebServer.a(WebAuthentication.cpp.o): in function `getMD5(unsigned char*, unsigned short, char*)’:
C:\Respaldo_MacBookPro\Arduino\ESP_Web_Server_Course\1_2_Hello_World_WS_SPIFFS/.pio/libdeps/esp32doit-devkit-v1/ESP Async WebServer/src/WebAuthentication.cpp:73: undefined reference to `mbedtls_md5_starts’
collect2.exe: error: ld returned 1 exit status
*** [.pio\build\esp32doit-devkit-v1\firmware.elf] Error 1.
 
A similar message appeared for example 2_1_Output
 

Hi.
Please take a look at pages 188-190.
I suggestion using Option 2 or Option 3 to fix the issue.
 
Let me know if this solves the problem or if you need further help.
 
Regards,
Sara

Dear Sara problem solved. My mistake for not reading in depth the book. Obrigado
I’d like to add that this is the first book, on the issue,  with a proper pedagogical structure, with clarity and easy to follow, congratulations.
 
Kind regards

That’s great. I’m glad you’re enjoying the ebook.
I‘ll mark this issue as resolved. If you need further help, you just need to open a new question in our forum.
 
Regards.
Sara