Two persons are in a house and one asks,
"can we go outside?"
"can we come outside?"
Which of the two questions is better?
'come' is used when your suggested direction of movement is towards the person you are talking to. 'go' works the opposite way in this respect.
Can we come outside? -- The hearer is outside and 'we' are inside. 'We' would like to move towards the hearer: outside.
Can we go outside? -- The hearer and the speaker are inside. The speaker wants to go in a different direction or away from the hearer: outside.
Both sentences are possible in their relevant extralinguistic contexts.