How does "Farewell to Lieutenant Du for Shu" express the author's feelings?

Du Shaofu is a good friend of Wang Bo. This poem was written by Wang Bo for his friend to go to Zhoushudang county magistrate. Du Shaofu, surnamed Du Shaofu, is an official name, and is a respectful name for the county captain. He took office. Zhou Shu, also known as "Shuchuan", is now Chongqing in Sichuan.

This poem is a farewell poem. When leaving, Wang Bo advised Du Shaofu not to be sad for leaving. He believes that as long as their friendship is sincere, even though they are thousands of miles away from Qian Shan, they are like close neighbors. At the same time, it also expresses the author's nostalgia for his friends' long journey, encourages them to be optimistic and enterprising, and bravely welcomes a new life, which embodies the author's broad mind and lofty aspirations.