I learn that "long to" is "want desperately to" in dictionary. Then, can I understand "be" in "where I long to be" as "go"?
Good question! "Place I long to be" can be understood as "the place I desperately long to be in/at," as the "be" in this line can be understood as "be in" or "at" (place). It is slightly different from "go." Ex: I long to be in Paris right now. Ex: A: Where do you long to be? B: On a nice sunny beach somewhere.