The phrase "go forth" can be substituted by a number of synonyms, each of which can convey a slightly different meaning. Some common alternatives include: proceed, advance, head out, move forward, depart, set off, venture, start, initiate, launch, begin, and embark. Depending on the context, some of these synonyms may be more appropriate than others. For example, "begin" might be a better fit when talking about starting a new project, while "set off" is often used to talk about a journey or trip. Whatever the situation, these synonyms provide a range of options for expressing the idea of moving forward in some way.